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	$41.83	10.425%	$46.1908	$46.19	$46.20	$46.20
Purchase #2	$142.65	8.572%	$154.878	$154.88	$154.90	$154.90
Purchase #3	$87.93	13.132%	$99.477	$99.48	$99.50	$99.50
Purchase #4	$191.38	4.771%	$200.5107	$200.51	$200.50	$200.50
Purchase #5	$119.48	3.168%	$123.2651	$123.27	$123.25	$123.30
Purchase #6	$73.38	4.149%	$76.4245	$76.42	$76.40	$76.40
Purchase #7	$208.41	12.480%	$234.4196	$234.42	$234.40	$234.40
7 purchase totals =	$865.06		$935.1657	$935.17	$935.15	$935.20