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	$169.91	7.392%	$182.4697	$182.47	$182.45	$182.50
Purchase #2	$39.90	11.718%	$44.5755	$44.58	$44.60	$44.60
Purchase #3	$216.86	11.685%	$242.2001	$242.20	$242.20	$242.20
Purchase #4	$35.83	13.215%	$40.5649	$40.56	$40.55	$40.60
Purchase #5	$126.25	5.784%	$133.5523	$133.55	$133.55	$133.60
Purchase #6	$189.41	11.831%	$211.8191	$211.82	$211.80	$211.80
Purchase #7	$197.27	9.525%	$216.06	$216.06	$216.05	$216.10
7 purchase totals =	$975.43		$1,071.2416	$1,071.24	$1,071.20	$1,071.40