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	$60.71	10.642%	$67.1708	$67.17	$67.15	$67.20
Purchase #2	$198.35	12.663%	$223.4671	$223.47	$223.45	$223.50
Purchase #3	$119.30	9.858%	$131.0606	$131.06	$131.05	$131.10
Purchase #4	$63.30	3.489%	$65.5085	$65.51	$65.50	$65.50
Purchase #5	$52.49	8.502%	$56.9527	$56.95	$56.95	$57.00
Purchase #6	$134.93	9.374%	$147.5783	$147.58	$147.60	$147.60
Purchase #7	$218.32	12.525%	$245.6646	$245.66	$245.65	$245.70
7 purchase totals =	$847.40		$937.4026	$937.40	$937.35	$937.60