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	$189.73	10.340%	$209.3481	$209.35	$209.35	$209.30
Purchase #2	$72.36	8.820%	$78.7422	$78.74	$78.75	$78.70
Purchase #3	$64.31	11.700%	$71.8343	$71.83	$71.85	$71.80
Purchase #4	$114.67	11.684%	$128.068	$128.07	$128.05	$128.10
Purchase #5	$184.88	4.519%	$193.2347	$193.23	$193.25	$193.20
Purchase #6	$128.25	8.111%	$138.6524	$138.65	$138.65	$138.70
Purchase #7	$197.39	8.207%	$213.5898	$213.59	$213.60	$213.60
7 purchase totals =	$951.59		$1,033.4695	$1,033.46	$1,033.50	$1,033.40