Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$173.79	11.658%	$194.0504	$194.05	$194.05	$194.10
Purchase #2	$171.96	7.363%	$184.6214	$184.62	$184.60	$184.60
Purchase #3	$118.31	11.142%	$131.4921	$131.49	$131.50	$131.50
Purchase #4	$140.60	4.616%	$147.0901	$147.09	$147.10	$147.10
Purchase #5	$221.73	5.187%	$233.2311	$233.23	$233.25	$233.20
Purchase #6	$94.59	11.710%	$105.6665	$105.67	$105.65	$105.70
Purchase #7	$195.89	12.124%	$219.6397	$219.64	$219.65	$219.60
7 purchase totals =	$1,116.87		$1,215.7913	$1,215.79	$1,215.80	$1,215.80