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	$38.35	12.146%	$43.008	$43.01	$43.00	$43.00
Purchase #2	$84.39	5.855%	$89.331	$89.33	$89.35	$89.30
Purchase #3	$92.28	10.372%	$101.8513	$101.85	$101.85	$101.90
Purchase #4	$234.69	9.172%	$256.2158	$256.22	$256.20	$256.20
Purchase #5	$219.47	6.641%	$234.045	$234.05	$234.05	$234.00
Purchase #6	$130.88	12.657%	$147.4455	$147.45	$147.45	$147.40
Purchase #7	$77.63	7.285%	$83.2853	$83.29	$83.30	$83.30
7 purchase totals =	$877.69		$955.1819	$955.20	$955.20	$955.10