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	$77.78	5.675%	$82.194	$82.19	$82.20	$82.20
Purchase #2	$97.82	7.805%	$105.4549	$105.45	$105.45	$105.50
Purchase #3	$100.43	5.215%	$105.6674	$105.67	$105.65	$105.70
Purchase #4	$120.52	7.837%	$129.9652	$129.97	$129.95	$130.00
Purchase #5	$112.81	4.442%	$117.821	$117.82	$117.80	$117.80
Purchase #6	$230.49	5.808%	$243.8769	$243.88	$243.90	$243.90
Purchase #7	$205.31	6.419%	$218.4888	$218.49	$218.50	$218.50
7 purchase totals =	$945.16		$1,003.4682	$1,003.47	$1,003.45	$1,003.60