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	$54.78	5.137%	$57.594	$57.59	$57.60	$57.60
Purchase #2	$126.72	3.510%	$131.1679	$131.17	$131.15	$131.20
Purchase #3	$231.73	11.387%	$258.1171	$258.12	$258.10	$258.10
Purchase #4	$99.96	11.154%	$111.1095	$111.11	$111.10	$111.10
Purchase #5	$46.31	7.524%	$49.7944	$49.79	$49.80	$49.80
Purchase #6	$191.50	8.140%	$207.0881	$207.09	$207.10	$207.10
Purchase #7	$55.93	6.495%	$59.5627	$59.56	$59.55	$59.60
7 purchase totals =	$806.93		$874.4337	$874.43	$874.40	$874.50