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	$48.30	8.820%	$52.5601	$52.56	$52.55	$52.60
Purchase #2	$184.88	8.677%	$200.922	$200.92	$200.90	$200.90
Purchase #3	$65.81	9.166%	$71.8421	$71.84	$71.85	$71.80
Purchase #4	$46.90	12.488%	$52.7569	$52.76	$52.75	$52.80
Purchase #5	$180.54	10.868%	$200.1611	$200.16	$200.15	$200.20
Purchase #6	$49.57	5.265%	$52.1799	$52.18	$52.20	$52.20
Purchase #7	$169.94	4.253%	$177.1675	$177.17	$177.15	$177.20
7 purchase totals =	$745.94		$807.5896	$807.59	$807.55	$807.70