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	$76.41	9.564%	$83.7179	$83.72	$83.70	$83.70
Purchase #2	$193.75	13.316%	$219.5498	$219.55	$219.55	$219.50
Purchase #3	$141.43	7.417%	$151.9199	$151.92	$151.90	$151.90
Purchase #4	$69.41	6.312%	$73.7912	$73.79	$73.80	$73.80
Purchase #5	$139.40	4.531%	$145.7162	$145.72	$145.70	$145.70
Purchase #6	$142.59	5.753%	$150.7932	$150.79	$150.80	$150.80
Purchase #7	$91.53	10.124%	$100.7965	$100.80	$100.80	$100.80
7 purchase totals =	$854.52		$926.2847	$926.29	$926.25	$926.20