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	$110.35	10.720%	$122.1795	$122.18	$122.20	$122.20
Purchase #2	$85.32	6.466%	$90.8368	$90.84	$90.85	$90.80
Purchase #3	$164.74	12.778%	$185.7905	$185.79	$185.80	$185.80
Purchase #4	$142.94	6.404%	$152.0939	$152.09	$152.10	$152.10
Purchase #5	$240.92	13.619%	$273.7309	$273.73	$273.75	$273.70
Purchase #6	$80.76	6.274%	$85.8269	$85.83	$85.85	$85.80
Purchase #7	$191.43	7.592%	$205.9634	$205.96	$205.95	$206.00
7 purchase totals =	$1,016.46		$1,116.4219	$1,116.42	$1,116.50	$1,116.40