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	$169.38	13.199%	$191.7365	$191.74	$191.75	$191.70
Purchase #2	$127.88	10.286%	$141.0337	$141.03	$141.05	$141.00
Purchase #3	$53.89	7.791%	$58.0886	$58.09	$58.10	$58.10
Purchase #4	$111.61	6.255%	$118.5912	$118.59	$118.60	$118.60
Purchase #5	$82.41	4.248%	$85.9108	$85.91	$85.90	$85.90
Purchase #6	$196.31	13.307%	$222.433	$222.43	$222.45	$222.40
Purchase #7	$61.58	3.792%	$63.9151	$63.92	$63.90	$63.90
7 purchase totals =	$803.06		$881.7089	$881.71	$881.75	$881.60