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	$77.54	5.821%	$82.0536	$82.05	$82.05	$82.10
Purchase #2	$10.83	13.463%	$12.288	$12.29	$12.30	$12.30
Purchase #3	$147.89	7.870%	$159.5289	$159.53	$159.55	$159.50
Purchase #4	$69.25	3.781%	$71.8683	$71.87	$71.85	$71.90
Purchase #5	$187.58	5.792%	$198.4446	$198.44	$198.45	$198.40
Purchase #6	$42.76	5.783%	$45.2328	$45.23	$45.25	$45.20
Purchase #7	$153.57	7.743%	$165.4609	$165.46	$165.45	$165.50
7 purchase totals =	$689.42		$734.8771	$734.87	$734.90	$734.90