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	$147.35	11.512%	$164.3129	$164.31	$164.30	$164.30
Purchase #2	$28.89	13.247%	$32.7171	$32.72	$32.70	$32.70
Purchase #3	$135.61	7.784%	$146.1659	$146.17	$146.15	$146.20
Purchase #4	$196.33	6.667%	$209.4193	$209.42	$209.40	$209.40
Purchase #5	$126.66	13.189%	$143.3652	$143.37	$143.35	$143.40
Purchase #6	$170.98	11.179%	$190.0939	$190.09	$190.10	$190.10
Purchase #7	$149.35	13.357%	$169.2987	$169.30	$169.30	$169.30
7 purchase totals =	$955.17		$1,055.3730	$1,055.38	$1,055.30	$1,055.40