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	$203.44	7.185%	$218.0572	$218.06	$218.05	$218.10
Purchase #2	$128.78	5.513%	$135.8796	$135.88	$135.90	$135.90
Purchase #3	$137.71	9.102%	$150.2444	$150.24	$150.25	$150.20
Purchase #4	$89.47	12.740%	$100.8685	$100.87	$100.85	$100.90
Purchase #5	$184.61	4.502%	$192.9211	$192.92	$192.90	$192.90
Purchase #6	$242.75	6.601%	$258.7739	$258.77	$258.75	$258.80
Purchase #7	$119.85	7.410%	$128.7309	$128.73	$128.75	$128.70
7 purchase totals =	$1,106.61		$1,185.4756	$1,185.47	$1,185.45	$1,185.50