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	$127.62	6.178%	$135.5044	$135.50	$135.50	$135.50
Purchase #2	$166.90	5.113%	$175.4336	$175.43	$175.45	$175.40
Purchase #3	$56.38	8.394%	$61.1125	$61.11	$61.10	$61.10
Purchase #4	$52.88	12.201%	$59.3319	$59.33	$59.35	$59.30
Purchase #5	$85.60	13.187%	$96.8881	$96.89	$96.90	$96.90
Purchase #6	$234.98	8.689%	$255.3974	$255.40	$255.40	$255.40
Purchase #7	$144.62	5.561%	$152.6623	$152.66	$152.65	$152.70
7 purchase totals =	$868.98		$936.3302	$936.32	$936.35	$936.30