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	$227.92	5.512%	$240.483	$240.48	$240.50	$240.50
Purchase #2	$105.39	6.208%	$111.9326	$111.93	$111.95	$111.90
Purchase #3	$202.65	3.253%	$209.2422	$209.24	$209.25	$209.20
Purchase #4	$182.89	4.771%	$191.6157	$191.62	$191.60	$191.60
Purchase #5	$115.73	7.417%	$124.3137	$124.31	$124.30	$124.30
Purchase #6	$85.60	10.696%	$94.7558	$94.76	$94.75	$94.80
Purchase #7	$208.51	5.201%	$219.3546	$219.35	$219.35	$219.40
7 purchase totals =	$1,128.69		$1,191.6976	$1,191.69	$1,191.70	$1,191.70