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	$165.78	6.625%	$176.7629	$176.76	$176.75	$176.80
Purchase #2	$55.51	11.707%	$62.0086	$62.01	$62.00	$62.00
Purchase #3	$122.30	7.847%	$131.8969	$131.90	$131.90	$131.90
Purchase #4	$46.66	7.418%	$50.1212	$50.12	$50.10	$50.10
Purchase #5	$78.73	6.662%	$83.975	$83.98	$84.00	$84.00
Purchase #6	$64.89	8.578%	$70.4563	$70.46	$70.45	$70.50
Purchase #7	$94.33	6.528%	$100.4879	$100.49	$100.50	$100.50
7 purchase totals =	$628.20		$675.7088	$675.72	$675.70	$675.80