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	$203.56	10.598%	$225.1333	$225.13	$225.15	$225.10
Purchase #2	$194.27	7.104%	$208.0709	$208.07	$208.05	$208.10
Purchase #3	$139.71	4.203%	$145.582	$145.58	$145.60	$145.60
Purchase #4	$100.50	8.508%	$109.0505	$109.05	$109.05	$109.10
Purchase #5	$150.84	13.438%	$171.1099	$171.11	$171.10	$171.10
Purchase #6	$65.28	9.204%	$71.2884	$71.29	$71.30	$71.30
Purchase #7	$55.77	11.701%	$62.2956	$62.30	$62.30	$62.30
7 purchase totals =	$909.93		$992.5306	$992.53	$992.55	$992.60