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	$224.39	5.569%	$236.8863	$236.89	$236.90	$236.90
Purchase #2	$92.63	7.801%	$99.8561	$99.86	$99.85	$99.90
Purchase #3	$102.33	12.104%	$114.716	$114.72	$114.70	$114.70
Purchase #4	$58.90	10.656%	$65.1764	$65.18	$65.20	$65.20
Purchase #5	$69.30	13.781%	$78.8502	$78.85	$78.85	$78.90
Purchase #6	$243.60	10.231%	$268.5227	$268.52	$268.50	$268.50
Purchase #7	$160.79	10.372%	$177.4671	$177.47	$177.45	$177.50
7 purchase totals =	$951.94		$1,041.4748	$1,041.49	$1,041.45	$1,041.60