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	$76.50	13.401%	$86.7518	$86.75	$86.75	$86.80
Purchase #2	$91.35	11.153%	$101.5383	$101.54	$101.55	$101.50
Purchase #3	$244.80	7.473%	$263.0939	$263.09	$263.10	$263.10
Purchase #4	$250.46	7.446%	$269.1093	$269.11	$269.10	$269.10
Purchase #5	$99.53	11.805%	$111.2795	$111.28	$111.30	$111.30
Purchase #6	$18.68	7.741%	$20.126	$20.13	$20.15	$20.10
Purchase #7	$35.32	6.681%	$37.6797	$37.68	$37.70	$37.70
7 purchase totals =	$816.64		$889.5785	$889.58	$889.65	$889.60