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	$180.55	5.318%	$190.1516	$190.15	$190.15	$190.20
Purchase #2	$105.59	5.283%	$111.1683	$111.17	$111.15	$111.20
Purchase #3	$33.71	10.190%	$37.145	$37.15	$37.15	$37.10
Purchase #4	$84.31	7.235%	$90.4098	$90.41	$90.40	$90.40
Purchase #5	$119.76	7.279%	$128.4773	$128.48	$128.50	$128.50
Purchase #6	$223.71	4.552%	$233.8933	$233.89	$233.90	$233.90
Purchase #7	$183.98	10.228%	$202.7975	$202.80	$202.80	$202.80
7 purchase totals =	$931.61		$994.0428	$994.05	$994.05	$994.10