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	$85.50	5.740%	$90.4077	$90.41	$90.40	$90.40
Purchase #2	$174.73	9.696%	$191.6718	$191.67	$191.65	$191.70
Purchase #3	$63.33	8.282%	$68.575	$68.58	$68.60	$68.60
Purchase #4	$233.58	11.175%	$259.6826	$259.68	$259.70	$259.70
Purchase #5	$63.43	5.436%	$66.8781	$66.88	$66.90	$66.90
Purchase #6	$93.90	7.338%	$100.7904	$100.79	$100.80	$100.80
Purchase #7	$215.88	4.439%	$225.4629	$225.46	$225.45	$225.50
7 purchase totals =	$930.35		$1,003.4685	$1,003.47	$1,003.50	$1,003.60