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	$207.56	12.472%	$233.4469	$233.45	$233.45	$233.40
Purchase #2	$53.91	4.826%	$56.5117	$56.51	$56.50	$56.50
Purchase #3	$6.57	12.488%	$7.3905	$7.39	$7.40	$7.40
Purchase #4	$32.40	9.274%	$35.4048	$35.40	$35.40	$35.40
Purchase #5	$153.39	13.865%	$174.6575	$174.66	$174.65	$174.70
Purchase #6	$29.54	8.137%	$31.9437	$31.94	$31.95	$31.90
Purchase #7	$85.67	10.318%	$94.5094	$94.51	$94.50	$94.50
7 purchase totals =	$569.04		$633.8645	$633.86	$633.85	$633.80