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	$250.89	5.395%	$264.4255	$264.43	$264.45	$264.40
Purchase #2	$120.31	11.791%	$134.4958	$134.50	$134.50	$134.50
Purchase #3	$86.53	8.395%	$93.7942	$93.79	$93.80	$93.80
Purchase #4	$143.27	12.181%	$160.7217	$160.72	$160.70	$160.70
Purchase #5	$146.73	5.710%	$155.1083	$155.11	$155.10	$155.10
Purchase #6	$102.41	9.326%	$111.9608	$111.96	$111.95	$112.00
Purchase #7	$147.34	12.819%	$166.2275	$166.23	$166.25	$166.20
7 purchase totals =	$997.48		$1,086.7338	$1,086.74	$1,086.75	$1,086.70