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	$119.27	4.607%	$124.7648	$124.76	$124.75	$124.80
Purchase #2	$197.70	8.579%	$214.6607	$214.66	$214.65	$214.70
Purchase #3	$73.69	5.169%	$77.499	$77.50	$77.50	$77.50
Purchase #4	$197.40	4.521%	$206.3245	$206.32	$206.30	$206.30
Purchase #5	$79.95	7.299%	$85.7856	$85.79	$85.80	$85.80
Purchase #6	$111.92	10.269%	$123.4131	$123.41	$123.40	$123.40
Purchase #7	$230.39	8.739%	$250.5238	$250.52	$250.50	$250.50
7 purchase totals =	$1,010.32		$1,082.9715	$1,082.96	$1,082.90	$1,083.00