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	$106.29	3.268%	$109.7636	$109.76	$109.75	$109.80
Purchase #2	$148.40	6.319%	$157.7774	$157.78	$157.80	$157.80
Purchase #3	$53.54	6.662%	$57.1068	$57.11	$57.10	$57.10
Purchase #4	$150.35	3.646%	$155.8318	$155.83	$155.85	$155.80
Purchase #5	$9.28	9.348%	$10.1475	$10.15	$10.15	$10.10
Purchase #6	$57.41	3.200%	$59.2471	$59.25	$59.25	$59.20
Purchase #7	$161.84	4.711%	$169.4643	$169.46	$169.45	$169.50
7 purchase totals =	$687.11		$719.3385	$719.34	$719.35	$719.30