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	$233.50	12.858%	$263.5234	$263.52	$263.50	$263.50
Purchase #2	$165.99	13.719%	$188.7622	$188.76	$188.75	$188.80
Purchase #3	$49.80	9.551%	$54.5564	$54.56	$54.55	$54.60
Purchase #4	$35.67	11.228%	$39.675	$39.68	$39.70	$39.70
Purchase #5	$72.41	10.833%	$80.2542	$80.25	$80.25	$80.30
Purchase #6	$237.62	12.759%	$267.9379	$267.94	$267.95	$267.90
Purchase #7	$205.61	11.431%	$229.1133	$229.11	$229.10	$229.10
7 purchase totals =	$1,000.60		$1,123.8224	$1,123.82	$1,123.80	$1,123.90