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	$127.63	11.188%	$141.9092	$141.91	$141.90	$141.90
Purchase #2	$58.67	3.139%	$60.5117	$60.51	$60.50	$60.50
Purchase #3	$142.50	12.104%	$159.7482	$159.75	$159.75	$159.70
Purchase #4	$188.40	5.670%	$199.0823	$199.08	$199.10	$199.10
Purchase #5	$168.55	12.793%	$190.1126	$190.11	$190.10	$190.10
Purchase #6	$235.46	10.277%	$259.6582	$259.66	$259.65	$259.70
Purchase #7	$59.36	3.521%	$61.4501	$61.45	$61.45	$61.50
7 purchase totals =	$980.57		$1,072.4723	$1,072.47	$1,072.45	$1,072.50