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	$153.82	7.644%	$165.578	$165.58	$165.60	$165.60
Purchase #2	$220.57	13.633%	$250.6403	$250.64	$250.65	$250.60
Purchase #3	$215.32	3.550%	$222.9639	$222.96	$222.95	$223.00
Purchase #4	$150.89	12.625%	$169.9399	$169.94	$169.95	$169.90
Purchase #5	$245.56	3.726%	$254.7096	$254.71	$254.70	$254.70
Purchase #6	$131.52	8.611%	$142.8452	$142.85	$142.85	$142.80
Purchase #7	$53.87	12.144%	$60.412	$60.41	$60.40	$60.40
7 purchase totals =	$1,171.55		$1,267.0889	$1,267.09	$1,267.10	$1,267.00