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	$117.37	9.137%	$128.0941	$128.09	$128.10	$128.10
Purchase #2	$41.73	9.511%	$45.6989	$45.70	$45.70	$45.70
Purchase #3	$10.77	7.744%	$11.604	$11.60	$11.60	$11.60
Purchase #4	$89.71	11.844%	$100.3353	$100.34	$100.35	$100.30
Purchase #5	$52.90	12.561%	$59.5448	$59.54	$59.55	$59.50
Purchase #6	$65.84	8.280%	$71.2916	$71.29	$71.30	$71.30
Purchase #7	$36.30	11.355%	$40.4219	$40.42	$40.40	$40.40
7 purchase totals =	$414.62		$456.9906	$456.98	$457.00	$456.90