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	$225.27	10.368%	$248.626	$248.63	$248.65	$248.60
Purchase #2	$99.94	5.333%	$105.2698	$105.27	$105.25	$105.30
Purchase #3	$141.65	10.504%	$156.5289	$156.53	$156.55	$156.50
Purchase #4	$203.38	9.313%	$222.3208	$222.32	$222.30	$222.30
Purchase #5	$203.34	11.791%	$227.3158	$227.32	$227.30	$227.30
Purchase #6	$128.77	11.327%	$143.3558	$143.36	$143.35	$143.40
Purchase #7	$7.98	4.829%	$8.3654	$8.37	$8.35	$8.40
7 purchase totals =	$1,010.33		$1,111.7825	$1,111.80	$1,111.75	$1,111.80