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	$114.95	13.643%	$130.6326	$130.63	$130.65	$130.60
Purchase #2	$39.43	8.152%	$42.6443	$42.64	$42.65	$42.60
Purchase #3	$116.43	9.238%	$127.1858	$127.19	$127.20	$127.20
Purchase #4	$91.81	5.421%	$96.787	$96.79	$96.80	$96.80
Purchase #5	$243.85	10.133%	$268.5593	$268.56	$268.55	$268.60
Purchase #6	$89.57	13.301%	$101.4837	$101.48	$101.50	$101.50
Purchase #7	$170.64	5.540%	$180.0935	$180.09	$180.10	$180.10
7 purchase totals =	$866.68		$947.3862	$947.38	$947.45	$947.40