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	$211.42	6.663%	$225.5069	$225.51	$225.50	$225.50
Purchase #2	$112.95	12.646%	$127.2337	$127.23	$127.25	$127.20
Purchase #3	$71.53	10.217%	$78.8382	$78.84	$78.85	$78.80
Purchase #4	$33.30	7.109%	$35.6673	$35.67	$35.65	$35.70
Purchase #5	$168.98	11.555%	$188.5056	$188.51	$188.50	$188.50
Purchase #6	$183.57	13.806%	$208.9137	$208.91	$208.90	$208.90
Purchase #7	$96.61	7.275%	$103.6384	$103.64	$103.65	$103.60
7 purchase totals =	$878.36		$968.3038	$968.31	$968.30	$968.20