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	$212.79	7.538%	$228.8301	$228.83	$228.85	$228.80
Purchase #2	$189.77	10.310%	$209.3353	$209.34	$209.35	$209.30
Purchase #3	$218.47	10.870%	$242.2177	$242.22	$242.20	$242.20
Purchase #4	$107.84	8.130%	$116.6074	$116.61	$116.60	$116.60
Purchase #5	$19.49	4.682%	$20.4025	$20.40	$20.40	$20.40
Purchase #6	$107.29	6.772%	$114.5557	$114.56	$114.55	$114.60
Purchase #7	$250.90	3.465%	$259.5937	$259.59	$259.60	$259.60
7 purchase totals =	$1,106.55		$1,191.5424	$1,191.55	$1,191.55	$1,191.50