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	$93.76	12.420%	$105.405	$105.41	$105.40	$105.40
Purchase #2	$63.40	4.545%	$66.2815	$66.28	$66.30	$66.30
Purchase #3	$222.71	12.645%	$250.8717	$250.87	$250.85	$250.90
Purchase #4	$115.91	13.420%	$131.4651	$131.47	$131.45	$131.50
Purchase #5	$57.65	9.287%	$63.004	$63.00	$63.00	$63.00
Purchase #6	$152.69	13.190%	$172.8298	$172.83	$172.85	$172.80
Purchase #7	$212.77	13.833%	$242.2025	$242.20	$242.20	$242.20
7 purchase totals =	$918.89		$1,032.0596	$1,032.06	$1,032.05	$1,032.10