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	$146.28	5.738%	$154.6735	$154.67	$154.65	$154.70
Purchase #2	$74.35	10.446%	$82.1166	$82.12	$82.10	$82.10
Purchase #3	$241.32	11.787%	$269.7644	$269.76	$269.75	$269.80
Purchase #4	$125.48	11.467%	$139.8688	$139.87	$139.85	$139.90
Purchase #5	$249.33	8.804%	$271.281	$271.28	$271.30	$271.30
Purchase #6	$157.91	13.801%	$179.7032	$179.70	$179.70	$179.70
Purchase #7	$37.87	12.232%	$42.5023	$42.50	$42.50	$42.50
7 purchase totals =	$1,032.54		$1,139.9098	$1,139.90	$1,139.85	$1,140.00