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	$98.93	5.261%	$104.1347	$104.13	$104.15	$104.10
Purchase #2	$154.34	3.222%	$159.3128	$159.31	$159.30	$159.30
Purchase #3	$48.27	7.742%	$52.0071	$52.01	$52.00	$52.00
Purchase #4	$199.70	11.452%	$222.5696	$222.57	$222.55	$222.60
Purchase #5	$89.95	6.612%	$95.8975	$95.90	$95.90	$95.90
Purchase #6	$182.72	10.159%	$201.2825	$201.28	$201.30	$201.30
Purchase #7	$87.41	9.468%	$95.686	$95.69	$95.70	$95.70
7 purchase totals =	$861.32		$930.8902	$930.89	$930.90	$930.90