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	$223.74	13.141%	$253.1417	$253.14	$253.15	$253.10
Purchase #2	$36.43	3.112%	$37.5637	$37.56	$37.55	$37.60
Purchase #3	$33.73	11.181%	$37.5014	$37.50	$37.50	$37.50
Purchase #4	$184.46	5.869%	$195.286	$195.29	$195.30	$195.30
Purchase #5	$123.90	7.716%	$133.4601	$133.46	$133.45	$133.50
Purchase #6	$131.51	8.356%	$142.499	$142.50	$142.50	$142.50
Purchase #7	$88.95	12.192%	$99.7948	$99.79	$99.80	$99.80
7 purchase totals =	$822.72		$899.2467	$899.24	$899.25	$899.30