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	$127.48	11.806%	$142.5303	$142.53	$142.55	$142.50
Purchase #2	$142.33	9.369%	$155.6649	$155.66	$155.65	$155.70
Purchase #3	$75.72	7.684%	$81.5383	$81.54	$81.55	$81.50
Purchase #4	$19.83	11.135%	$22.0381	$22.04	$22.05	$22.00
Purchase #5	$90.70	6.542%	$96.6336	$96.63	$96.65	$96.60
Purchase #6	$33.59	12.253%	$37.7058	$37.71	$37.70	$37.70
Purchase #7	$194.92	11.594%	$217.519	$217.52	$217.50	$217.50
7 purchase totals =	$684.57		$753.6300	$753.63	$753.65	$753.50