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	$88.33	4.556%	$92.3543	$92.35	$92.35	$92.40
Purchase #2	$34.43	7.361%	$36.9644	$36.96	$36.95	$37.00
Purchase #3	$78.47	4.788%	$82.2271	$82.23	$82.25	$82.20
Purchase #4	$188.84	10.363%	$208.4095	$208.41	$208.40	$208.40
Purchase #5	$201.78	11.432%	$224.8475	$224.85	$224.85	$224.80
Purchase #6	$124.44	10.852%	$137.9442	$137.94	$137.95	$137.90
Purchase #7	$173.47	13.160%	$196.2987	$196.30	$196.30	$196.30
7 purchase totals =	$889.76		$979.0457	$979.04	$979.05	$979.00