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	$123.47	11.496%	$137.6641	$137.66	$137.65	$137.70
Purchase #2	$197.47	11.317%	$219.8177	$219.82	$219.80	$219.80
Purchase #3	$146.97	10.417%	$162.2799	$162.28	$162.30	$162.30
Purchase #4	$248.69	6.188%	$264.0789	$264.08	$264.10	$264.10
Purchase #5	$156.49	5.776%	$165.5289	$165.53	$165.55	$165.50
Purchase #6	$240.67	6.158%	$255.4905	$255.49	$255.50	$255.50
Purchase #7	$176.74	5.245%	$186.01	$186.01	$186.00	$186.00
7 purchase totals =	$1,290.50		$1,390.8700	$1,390.87	$1,390.90	$1,390.90