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	$152.99	4.165%	$159.362	$159.36	$159.35	$159.40
Purchase #2	$54.40	9.582%	$59.6126	$59.61	$59.60	$59.60
Purchase #3	$118.51	8.707%	$128.8287	$128.83	$128.85	$128.80
Purchase #4	$97.52	6.388%	$103.7496	$103.75	$103.75	$103.70
Purchase #5	$12.28	10.357%	$13.5518	$13.55	$13.55	$13.60
Purchase #6	$205.98	7.559%	$221.55	$221.55	$221.55	$221.60
Purchase #7	$59.26	4.437%	$61.8894	$61.89	$61.90	$61.90
7 purchase totals =	$700.94		$748.5441	$748.54	$748.55	$748.60