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	$63.70	13.543%	$72.3269	$72.33	$72.35	$72.30
Purchase #2	$243.52	8.323%	$263.7882	$263.79	$263.80	$263.80
Purchase #3	$91.71	3.214%	$94.6576	$94.66	$94.65	$94.70
Purchase #4	$130.76	13.123%	$147.9196	$147.92	$147.90	$147.90
Purchase #5	$220.53	7.676%	$237.4579	$237.46	$237.45	$237.50
Purchase #6	$85.70	8.142%	$92.6777	$92.68	$92.70	$92.70
Purchase #7	$139.32	9.642%	$152.7532	$152.75	$152.75	$152.80
7 purchase totals =	$975.24		$1,061.5811	$1,061.59	$1,061.60	$1,061.70