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	$193.98	9.165%	$211.7583	$211.76	$211.75	$211.80
Purchase #2	$66.52	7.221%	$71.3234	$71.32	$71.30	$71.30
Purchase #3	$192.96	11.296%	$214.7568	$214.76	$214.75	$214.80
Purchase #4	$90.30	11.735%	$100.8967	$100.90	$100.90	$100.90
Purchase #5	$81.55	9.350%	$89.1749	$89.17	$89.15	$89.20
Purchase #6	$157.79	9.558%	$172.8716	$172.87	$172.85	$172.90
Purchase #7	$49.36	5.588%	$52.1182	$52.12	$52.10	$52.10
7 purchase totals =	$832.46		$912.8999	$912.90	$912.80	$913.00