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	$89.76	12.213%	$100.7224	$100.72	$100.70	$100.70
Purchase #2	$214.88	10.816%	$238.1214	$238.12	$238.10	$238.10
Purchase #3	$198.58	4.840%	$208.1913	$208.19	$208.20	$208.20
Purchase #4	$134.78	13.476%	$152.943	$152.94	$152.95	$152.90
Purchase #5	$41.69	12.319%	$46.8258	$46.83	$46.85	$46.80
Purchase #6	$206.75	9.412%	$226.2093	$226.21	$226.20	$226.20
Purchase #7	$114.32	4.520%	$119.4873	$119.49	$119.50	$119.50
7 purchase totals =	$1,000.76		$1,092.5005	$1,092.50	$1,092.50	$1,092.40