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	$73.93	13.413%	$83.8462	$83.85	$83.85	$83.80
Purchase #2	$173.28	13.644%	$196.9223	$196.92	$196.90	$196.90
Purchase #3	$63.27	11.744%	$70.7004	$70.70	$70.70	$70.70
Purchase #4	$95.37	13.686%	$108.4223	$108.42	$108.40	$108.40
Purchase #5	$49.33	3.163%	$50.8903	$50.89	$50.90	$50.90
Purchase #6	$111.68	11.174%	$124.1591	$124.16	$124.15	$124.20
Purchase #7	$217.47	3.369%	$224.7966	$224.80	$224.80	$224.80
7 purchase totals =	$784.33		$859.7372	$859.74	$859.70	$859.70