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	$175.54	6.609%	$187.1414	$187.14	$187.15	$187.10
Purchase #2	$113.45	9.123%	$123.8	$123.80	$123.80	$123.80
Purchase #3	$182.43	11.552%	$203.5043	$203.50	$203.50	$203.50
Purchase #4	$117.50	13.330%	$133.1628	$133.16	$133.15	$133.20
Purchase #5	$28.92	12.774%	$32.6142	$32.61	$32.60	$32.60
Purchase #6	$173.56	9.217%	$189.557	$189.56	$189.55	$189.60
Purchase #7	$136.98	9.336%	$149.7685	$149.77	$149.75	$149.80
7 purchase totals =	$928.38		$1,019.5482	$1,019.54	$1,019.50	$1,019.60