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	$37.56	11.392%	$41.8388	$41.84	$41.85	$41.80
Purchase #2	$146.58	12.688%	$165.1781	$165.18	$165.20	$165.20
Purchase #3	$168.89	4.146%	$175.8922	$175.89	$175.90	$175.90
Purchase #4	$236.57	10.237%	$260.7877	$260.79	$260.80	$260.80
Purchase #5	$141.76	9.361%	$155.0302	$155.03	$155.05	$155.00
Purchase #6	$55.68	3.731%	$57.7574	$57.76	$57.75	$57.80
Purchase #7	$215.51	10.444%	$238.0179	$238.02	$238.00	$238.00
7 purchase totals =	$1,002.55		$1,094.5023	$1,094.51	$1,094.55	$1,094.50