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	$124.33	5.371%	$131.0078	$131.01	$131.00	$131.00
Purchase #2	$93.55	6.221%	$99.3697	$99.37	$99.35	$99.40
Purchase #3	$168.54	11.764%	$188.367	$188.37	$188.35	$188.40
Purchase #4	$155.79	10.704%	$172.4658	$172.47	$172.45	$172.50
Purchase #5	$13.54	3.673%	$14.0373	$14.04	$14.05	$14.00
Purchase #6	$44.32	9.580%	$48.5659	$48.57	$48.55	$48.60
Purchase #7	$200.40	9.149%	$218.7346	$218.73	$218.75	$218.70
7 purchase totals =	$800.47		$872.5481	$872.56	$872.50	$872.60