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	$187.42	7.187%	$200.8899	$200.89	$200.90	$200.90
Purchase #2	$137.56	4.168%	$143.2935	$143.29	$143.30	$143.30
Purchase #3	$54.57	12.357%	$61.3132	$61.31	$61.30	$61.30
Purchase #4	$25.30	5.611%	$26.7196	$26.72	$26.70	$26.70
Purchase #5	$65.47	8.633%	$71.122	$71.12	$71.10	$71.10
Purchase #6	$119.47	13.302%	$135.3619	$135.36	$135.35	$135.40
Purchase #7	$151.81	3.139%	$156.5753	$156.58	$156.60	$156.60
7 purchase totals =	$741.60		$795.2754	$795.27	$795.25	$795.30