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	$193.45	12.826%	$218.2619	$218.26	$218.25	$218.30
Purchase #2	$108.89	5.525%	$114.9062	$114.91	$114.90	$114.90
Purchase #3	$140.29	10.103%	$154.4635	$154.46	$154.45	$154.50
Purchase #4	$244.29	6.781%	$260.8553	$260.86	$260.85	$260.90
Purchase #5	$97.53	13.827%	$111.0155	$111.02	$111.00	$111.00
Purchase #6	$130.50	7.690%	$140.5355	$140.54	$140.55	$140.50
Purchase #7	$96.49	6.404%	$102.6692	$102.67	$102.65	$102.70
7 purchase totals =	$1,011.44		$1,102.7071	$1,102.72	$1,102.65	$1,102.80