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	$67.49	3.483%	$69.8407	$69.84	$69.85	$69.80
Purchase #2	$91.84	8.363%	$99.5206	$99.52	$99.50	$99.50
Purchase #3	$34.98	7.803%	$37.7095	$37.71	$37.70	$37.70
Purchase #4	$85.91	7.412%	$92.2776	$92.28	$92.30	$92.30
Purchase #5	$104.87	6.561%	$111.7505	$111.75	$111.75	$111.80
Purchase #6	$237.70	5.739%	$251.3416	$251.34	$251.35	$251.30
Purchase #7	$61.82	7.399%	$66.3941	$66.39	$66.40	$66.40
7 purchase totals =	$684.61		$728.8346	$728.83	$728.85	$728.80