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	$233.37	10.858%	$258.7093	$258.71	$258.70	$258.70
Purchase #2	$149.77	11.155%	$166.4768	$166.48	$166.50	$166.50
Purchase #3	$222.95	9.530%	$244.1971	$244.20	$244.20	$244.20
Purchase #4	$129.68	4.403%	$135.3898	$135.39	$135.40	$135.40
Purchase #5	$105.30	6.471%	$112.114	$112.11	$112.10	$112.10
Purchase #6	$189.95	5.370%	$200.1503	$200.15	$200.15	$200.20
Purchase #7	$30.86	9.656%	$33.8398	$33.84	$33.85	$33.80
7 purchase totals =	$1,061.88		$1,150.8771	$1,150.88	$1,150.90	$1,150.90