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	$46.56	4.226%	$48.5276	$48.53	$48.55	$48.50
Purchase #2	$88.49	11.304%	$98.4929	$98.49	$98.50	$98.50
Purchase #3	$88.61	7.576%	$95.3231	$95.32	$95.30	$95.30
Purchase #4	$114.66	3.682%	$118.8818	$118.88	$118.90	$118.90
Purchase #5	$211.85	6.325%	$225.2495	$225.25	$225.25	$225.20
Purchase #6	$250.98	10.520%	$277.3831	$277.38	$277.40	$277.40
Purchase #7	$150.41	10.439%	$166.1113	$166.11	$166.10	$166.10
7 purchase totals =	$951.56		$1,029.9693	$1,029.96	$1,030.00	$1,029.90