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	$149.57	4.392%	$156.1391	$156.14	$156.15	$156.10
Purchase #2	$244.33	7.856%	$263.5246	$263.52	$263.50	$263.50
Purchase #3	$136.91	3.251%	$141.3609	$141.36	$141.35	$141.40
Purchase #4	$197.61	12.700%	$222.7065	$222.71	$222.70	$222.70
Purchase #5	$211.58	12.195%	$237.3822	$237.38	$237.40	$237.40
Purchase #6	$131.27	11.236%	$146.0195	$146.02	$146.00	$146.00
Purchase #7	$208.85	7.210%	$223.9081	$223.91	$223.90	$223.90
7 purchase totals =	$1,280.12		$1,391.0409	$1,391.04	$1,391.00	$1,391.00