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	$93.69	10.407%	$103.4403	$103.44	$103.45	$103.40
Purchase #2	$78.65	13.735%	$89.4526	$89.45	$89.45	$89.50
Purchase #3	$22.90	5.777%	$24.2229	$24.22	$24.20	$24.20
Purchase #4	$77.99	12.243%	$87.5383	$87.54	$87.55	$87.50
Purchase #5	$122.67	8.747%	$133.3999	$133.40	$133.40	$133.40
Purchase #6	$95.35	4.613%	$99.7485	$99.75	$99.75	$99.70
Purchase #7	$145.77	6.696%	$155.5308	$155.53	$155.55	$155.50
7 purchase totals =	$637.02		$693.3333	$693.33	$693.35	$693.20