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	$131.85	11.538%	$147.0629	$147.06	$147.05	$147.10
Purchase #2	$78.75	3.545%	$81.5417	$81.54	$81.55	$81.50
Purchase #3	$32.47	5.396%	$34.2221	$34.22	$34.20	$34.20
Purchase #4	$235.63	3.241%	$243.2668	$243.27	$243.25	$243.30
Purchase #5	$56.46	13.871%	$64.2916	$64.29	$64.30	$64.30
Purchase #6	$101.88	3.398%	$105.3419	$105.34	$105.35	$105.30
Purchase #7	$18.60	8.509%	$20.1827	$20.18	$20.20	$20.20
7 purchase totals =	$655.64		$695.9097	$695.90	$695.90	$695.90