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	$106.82	4.395%	$111.5147	$111.51	$111.50	$111.50
Purchase #2	$46.98	11.801%	$52.5241	$52.52	$52.50	$52.50
Purchase #3	$34.47	7.653%	$37.108	$37.11	$37.10	$37.10
Purchase #4	$97.85	11.690%	$109.2887	$109.29	$109.30	$109.30
Purchase #5	$152.31	11.151%	$169.2941	$169.29	$169.30	$169.30
Purchase #6	$57.63	6.408%	$61.3229	$61.32	$61.30	$61.30
Purchase #7	$152.50	9.301%	$166.684	$166.68	$166.70	$166.70
7 purchase totals =	$648.56		$707.7365	$707.72	$707.70	$707.70