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	$47.54	11.544%	$53.028	$53.03	$53.05	$53.00
Purchase #2	$28.96	7.232%	$31.0544	$31.05	$31.05	$31.10
Purchase #3	$50.47	3.871%	$52.4237	$52.42	$52.40	$52.40
Purchase #4	$136.82	10.685%	$151.4392	$151.44	$151.45	$151.40
Purchase #5	$221.73	4.374%	$231.4285	$231.43	$231.45	$231.40
Purchase #6	$16.55	11.102%	$18.3874	$18.39	$18.40	$18.40
Purchase #7	$186.87	5.125%	$196.4471	$196.45	$196.45	$196.40
7 purchase totals =	$688.94		$734.2083	$734.21	$734.25	$734.10