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	$250.84	7.373%	$269.3344	$269.33	$269.35	$269.30
Purchase #2	$22.96	12.489%	$25.8275	$25.83	$25.85	$25.80
Purchase #3	$33.89	9.578%	$37.136	$37.14	$37.15	$37.10
Purchase #4	$236.48	6.768%	$252.485	$252.49	$252.50	$252.50
Purchase #5	$116.89	5.809%	$123.6801	$123.68	$123.70	$123.70
Purchase #6	$143.46	5.118%	$150.8023	$150.80	$150.80	$150.80
Purchase #7	$25.71	5.635%	$27.1588	$27.16	$27.15	$27.20
7 purchase totals =	$830.23		$886.4241	$886.43	$886.50	$886.40