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	$42.99	5.349%	$45.2895	$45.29	$45.30	$45.30
Purchase #2	$159.84	13.166%	$180.8845	$180.88	$180.90	$180.90
Purchase #3	$150.42	13.829%	$171.2216	$171.22	$171.20	$171.20
Purchase #4	$232.43	4.671%	$243.2868	$243.29	$243.30	$243.30
Purchase #5	$92.36	3.514%	$95.6055	$95.61	$95.60	$95.60
Purchase #6	$71.84	3.861%	$74.6137	$74.61	$74.60	$74.60
Purchase #7	$209.62	6.123%	$222.455	$222.46	$222.45	$222.50
7 purchase totals =	$959.50		$1,033.3566	$1,033.36	$1,033.35	$1,033.40