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	$185.84	4.557%	$194.3087	$194.31	$194.30	$194.30
Purchase #2	$248.89	13.761%	$283.1398	$283.14	$283.15	$283.10
Purchase #3	$178.39	7.341%	$191.4856	$191.49	$191.50	$191.50
Purchase #4	$59.94	3.102%	$61.7993	$61.80	$61.80	$61.80
Purchase #5	$74.27	11.488%	$82.8021	$82.80	$82.80	$82.80
Purchase #6	$84.73	8.185%	$91.6652	$91.67	$91.65	$91.70
Purchase #7	$24.59	10.337%	$27.1319	$27.13	$27.15	$27.10
7 purchase totals =	$856.65		$932.3326	$932.34	$932.35	$932.30