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	$119.78	5.800%	$126.7272	$126.73	$126.75	$126.70
Purchase #2	$182.78	9.819%	$200.7272	$200.73	$200.75	$200.70
Purchase #3	$92.41	12.133%	$103.6221	$103.62	$103.60	$103.60
Purchase #4	$220.59	11.324%	$245.5696	$245.57	$245.55	$245.60
Purchase #5	$195.98	7.184%	$210.0592	$210.06	$210.05	$210.10
Purchase #6	$92.58	13.862%	$105.4134	$105.41	$105.40	$105.40
Purchase #7	$48.34	9.852%	$53.1025	$53.10	$53.10	$53.10
7 purchase totals =	$952.46		$1,045.2212	$1,045.22	$1,045.20	$1,045.20