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	$172.44	13.434%	$195.6056	$195.61	$195.60	$195.60
Purchase #2	$148.59	12.288%	$166.8487	$166.85	$166.85	$166.80
Purchase #3	$129.32	9.490%	$141.5925	$141.59	$141.60	$141.60
Purchase #4	$127.46	5.515%	$134.4894	$134.49	$134.50	$134.50
Purchase #5	$138.55	9.439%	$151.6277	$151.63	$151.65	$151.60
Purchase #6	$67.61	10.398%	$74.6401	$74.64	$74.65	$74.60
Purchase #7	$95.70	3.692%	$99.2332	$99.23	$99.25	$99.20
7 purchase totals =	$879.67		$964.0372	$964.04	$964.10	$963.90