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	$223.62	3.822%	$232.1668	$232.17	$232.15	$232.20
Purchase #2	$186.77	11.541%	$208.3251	$208.33	$208.35	$208.30
Purchase #3	$11.44	7.709%	$12.3219	$12.32	$12.30	$12.30
Purchase #4	$54.92	3.850%	$57.0344	$57.03	$57.05	$57.00
Purchase #5	$180.89	13.496%	$205.3029	$205.30	$205.30	$205.30
Purchase #6	$37.30	13.732%	$42.422	$42.42	$42.40	$42.40
Purchase #7	$199.89	7.289%	$214.46	$214.46	$214.45	$214.50
7 purchase totals =	$894.83		$972.0331	$972.03	$972.00	$972.00