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	$139.82	4.502%	$146.1147	$146.11	$146.10	$146.10
Purchase #2	$90.59	10.854%	$100.4226	$100.42	$100.40	$100.40
Purchase #3	$57.82	5.607%	$61.062	$61.06	$61.05	$61.10
Purchase #4	$133.79	8.173%	$144.7247	$144.72	$144.70	$144.70
Purchase #5	$191.61	3.224%	$197.7875	$197.79	$197.80	$197.80
Purchase #6	$198.50	7.470%	$213.328	$213.33	$213.35	$213.30
Purchase #7	$138.78	10.435%	$153.2617	$153.26	$153.25	$153.30
7 purchase totals =	$950.91		$1,016.7012	$1,016.69	$1,016.65	$1,016.70