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	$54.34	4.463%	$56.7652	$56.77	$56.75	$56.80
Purchase #2	$186.35	4.192%	$194.1618	$194.16	$194.15	$194.20
Purchase #3	$145.37	13.517%	$165.0197	$165.02	$165.00	$165.00
Purchase #4	$240.96	10.252%	$265.6632	$265.66	$265.65	$265.70
Purchase #5	$11.55	11.415%	$12.8684	$12.87	$12.85	$12.90
Purchase #6	$172.70	13.603%	$196.1924	$196.19	$196.20	$196.20
Purchase #7	$182.52	7.745%	$196.6562	$196.66	$196.65	$196.70
7 purchase totals =	$993.79		$1,087.3269	$1,087.33	$1,087.25	$1,087.50