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	$90.34	10.102%	$99.4661	$99.47	$99.45	$99.50
Purchase #2	$221.74	9.359%	$242.4926	$242.49	$242.50	$242.50
Purchase #3	$114.63	8.317%	$124.1638	$124.16	$124.15	$124.20
Purchase #4	$39.63	9.245%	$43.2938	$43.29	$43.30	$43.30
Purchase #5	$153.55	13.798%	$174.7368	$174.74	$174.75	$174.70
Purchase #6	$32.43	3.113%	$33.4395	$33.44	$33.45	$33.40
Purchase #7	$45.65	13.800%	$51.9497	$51.95	$51.95	$51.90
7 purchase totals =	$697.97		$769.5423	$769.54	$769.55	$769.50