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	$167.90	13.315%	$190.2559	$190.26	$190.25	$190.30
Purchase #2	$127.71	7.855%	$137.7416	$137.74	$137.75	$137.70
Purchase #3	$99.99	13.486%	$113.4747	$113.47	$113.45	$113.50
Purchase #4	$39.76	6.490%	$42.3404	$42.34	$42.35	$42.30
Purchase #5	$248.46	5.428%	$261.9464	$261.95	$261.95	$261.90
Purchase #6	$72.94	3.520%	$75.5075	$75.51	$75.50	$75.50
Purchase #7	$115.25	13.690%	$131.0277	$131.03	$131.05	$131.00
7 purchase totals =	$872.01		$952.2942	$952.30	$952.30	$952.20