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	$102.96	7.650%	$110.8364	$110.84	$110.85	$110.80
Purchase #2	$98.53	4.670%	$103.1314	$103.13	$103.15	$103.10
Purchase #3	$185.47	9.841%	$203.7221	$203.72	$203.70	$203.70
Purchase #4	$204.60	8.648%	$222.2938	$222.29	$222.30	$222.30
Purchase #5	$235.95	3.644%	$244.548	$244.55	$244.55	$244.50
Purchase #6	$189.29	5.860%	$200.3824	$200.38	$200.40	$200.40
Purchase #7	$53.52	3.616%	$55.4553	$55.46	$55.45	$55.50
7 purchase totals =	$1,070.32		$1,140.3694	$1,140.37	$1,140.40	$1,140.30