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	$115.49	7.414%	$124.0524	$124.05	$124.05	$124.10
Purchase #2	$132.54	10.418%	$146.348	$146.35	$146.35	$146.30
Purchase #3	$181.57	5.626%	$191.7851	$191.79	$191.80	$191.80
Purchase #4	$166.51	11.433%	$185.5471	$185.55	$185.55	$185.50
Purchase #5	$139.72	9.831%	$153.4559	$153.46	$153.45	$153.50
Purchase #6	$239.82	4.288%	$250.1035	$250.10	$250.10	$250.10
Purchase #7	$55.38	11.168%	$61.5648	$61.56	$61.55	$61.60
7 purchase totals =	$1,031.03		$1,112.8568	$1,112.86	$1,112.85	$1,112.90