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	$131.39	13.131%	$148.6428	$148.64	$148.65	$148.60
Purchase #2	$52.38	13.160%	$59.2732	$59.27	$59.25	$59.30
Purchase #3	$167.30	13.510%	$189.9022	$189.90	$189.90	$189.90
Purchase #4	$195.29	10.196%	$215.2018	$215.20	$215.20	$215.20
Purchase #5	$9.77	4.781%	$10.2371	$10.24	$10.25	$10.20
Purchase #6	$47.76	11.318%	$53.1655	$53.17	$53.15	$53.20
Purchase #7	$238.50	5.180%	$250.8543	$250.85	$250.85	$250.90
7 purchase totals =	$842.39		$927.2769	$927.27	$927.25	$927.30