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	$131.33	8.369%	$142.321	$142.32	$142.30	$142.30
Purchase #2	$78.75	5.146%	$82.8025	$82.80	$82.80	$82.80
Purchase #3	$93.90	5.516%	$99.0795	$99.08	$99.10	$99.10
Purchase #4	$73.83	3.823%	$76.6525	$76.65	$76.65	$76.70
Purchase #5	$46.64	8.825%	$50.756	$50.76	$50.75	$50.80
Purchase #6	$172.83	8.642%	$187.766	$187.77	$187.75	$187.80
Purchase #7	$73.34	11.689%	$81.9127	$81.91	$81.90	$81.90
7 purchase totals =	$670.62		$721.2902	$721.29	$721.25	$721.40