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	$11.76	4.785%	$12.3227	$12.32	$12.30	$12.30
Purchase #2	$182.61	7.686%	$196.6454	$196.65	$196.65	$196.60
Purchase #3	$46.89	5.687%	$49.5566	$49.56	$49.55	$49.60
Purchase #4	$185.47	12.294%	$208.2717	$208.27	$208.25	$208.30
Purchase #5	$45.33	12.457%	$50.9768	$50.98	$51.00	$51.00
Purchase #6	$204.61	9.432%	$223.9088	$223.91	$223.90	$223.90
Purchase #7	$247.71	5.699%	$261.827	$261.83	$261.85	$261.80
7 purchase totals =	$924.38		$1,003.5090	$1,003.52	$1,003.50	$1,003.50