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	$207.39	8.632%	$225.2919	$225.29	$225.30	$225.30
Purchase #2	$54.42	9.410%	$59.5409	$59.54	$59.55	$59.50
Purchase #3	$63.37	13.160%	$71.7095	$71.71	$71.70	$71.70
Purchase #4	$198.79	9.168%	$217.0151	$217.02	$217.00	$217.00
Purchase #5	$165.86	4.275%	$172.9505	$172.95	$172.95	$173.00
Purchase #6	$185.48	11.516%	$206.8399	$206.84	$206.85	$206.80
Purchase #7	$62.62	3.350%	$64.7178	$64.72	$64.70	$64.70
7 purchase totals =	$937.93		$1,018.0656	$1,018.07	$1,018.05	$1,018.00