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	$210.77	8.418%	$228.5126	$228.51	$228.50	$228.50
Purchase #2	$41.56	10.114%	$45.7634	$45.76	$45.75	$45.80
Purchase #3	$171.26	12.692%	$192.9963	$193.00	$193.00	$193.00
Purchase #4	$216.52	11.460%	$241.3332	$241.33	$241.35	$241.30
Purchase #5	$114.30	3.787%	$118.6285	$118.63	$118.65	$118.60
Purchase #6	$34.60	12.705%	$38.9959	$39.00	$39.00	$39.00
Purchase #7	$231.85	10.802%	$256.8944	$256.89	$256.90	$256.90
7 purchase totals =	$1,020.86		$1,123.1243	$1,123.12	$1,123.15	$1,123.10