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	$46.98	13.529%	$53.3359	$53.34	$53.35	$53.30
Purchase #2	$207.54	11.478%	$231.3614	$231.36	$231.35	$231.40
Purchase #3	$183.61	9.316%	$200.7151	$200.72	$200.70	$200.70
Purchase #4	$99.85	9.266%	$109.1021	$109.10	$109.10	$109.10
Purchase #5	$12.66	8.554%	$13.7429	$13.74	$13.75	$13.70
Purchase #6	$128.97	13.495%	$146.3745	$146.37	$146.35	$146.40
Purchase #7	$244.43	4.157%	$254.591	$254.59	$254.60	$254.60
7 purchase totals =	$924.04		$1,009.2229	$1,009.22	$1,009.20	$1,009.20