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	$61.71	8.655%	$67.051	$67.05	$67.05	$67.10
Purchase #2	$178.54	6.615%	$190.3504	$190.35	$190.35	$190.40
Purchase #3	$198.47	6.311%	$210.9954	$211.00	$211.00	$211.00
Purchase #4	$17.44	4.383%	$18.2044	$18.20	$18.20	$18.20
Purchase #5	$250.39	10.336%	$276.2703	$276.27	$276.25	$276.30
Purchase #6	$234.32	9.450%	$256.4632	$256.46	$256.45	$256.50
Purchase #7	$32.65	10.293%	$36.0107	$36.01	$36.00	$36.00
7 purchase totals =	$973.52		$1,055.3454	$1,055.34	$1,055.30	$1,055.50