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	$85.92	8.762%	$93.4483	$93.45	$93.45	$93.40
Purchase #2	$54.40	8.617%	$59.0876	$59.09	$59.10	$59.10
Purchase #3	$227.29	6.496%	$242.0548	$242.05	$242.05	$242.10
Purchase #4	$36.34	3.588%	$37.6439	$37.64	$37.65	$37.60
Purchase #5	$106.38	3.812%	$110.4352	$110.44	$110.45	$110.40
Purchase #6	$60.44	13.396%	$68.5365	$68.54	$68.55	$68.50
Purchase #7	$188.53	4.287%	$196.6123	$196.61	$196.60	$196.60
7 purchase totals =	$759.30		$807.8186	$807.82	$807.85	$807.70