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	$49.42	9.169%	$53.9513	$53.95	$53.95	$54.00
Purchase #2	$80.84	9.428%	$88.4616	$88.46	$88.45	$88.50
Purchase #3	$200.81	7.645%	$216.1619	$216.16	$216.15	$216.20
Purchase #4	$237.82	10.264%	$262.2298	$262.23	$262.25	$262.20
Purchase #5	$78.70	5.264%	$82.8428	$82.84	$82.85	$82.80
Purchase #6	$127.80	4.547%	$133.6111	$133.61	$133.60	$133.60
Purchase #7	$191.27	10.857%	$212.0362	$212.04	$212.05	$212.00
7 purchase totals =	$966.66		$1,049.2947	$1,049.29	$1,049.30	$1,049.30