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	$149.69	6.144%	$158.887	$158.89	$158.90	$158.90
Purchase #2	$249.29	8.475%	$270.4173	$270.42	$270.40	$270.40
Purchase #3	$33.41	5.212%	$35.1513	$35.15	$35.15	$35.20
Purchase #4	$225.99	12.199%	$253.5585	$253.56	$253.55	$253.60
Purchase #5	$176.82	10.833%	$195.9749	$195.97	$195.95	$196.00
Purchase #6	$34.47	9.142%	$37.6212	$37.62	$37.60	$37.60
Purchase #7	$198.31	12.207%	$222.5177	$222.52	$222.50	$222.50
7 purchase totals =	$1,067.98		$1,174.1279	$1,174.13	$1,174.05	$1,174.20