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	$144.33	8.703%	$156.891	$156.89	$156.90	$156.90
Purchase #2	$228.40	10.130%	$251.5369	$251.54	$251.55	$251.50
Purchase #3	$86.36	11.528%	$96.3156	$96.32	$96.30	$96.30
Purchase #4	$108.83	13.129%	$123.1183	$123.12	$123.10	$123.10
Purchase #5	$61.74	7.496%	$66.368	$66.37	$66.35	$66.40
Purchase #6	$172.38	4.234%	$179.6786	$179.68	$179.70	$179.70
Purchase #7	$58.78	9.785%	$64.5316	$64.53	$64.55	$64.50
7 purchase totals =	$860.82		$938.4400	$938.45	$938.45	$938.40