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	$218.26	3.463%	$225.8183	$225.82	$225.80	$225.80
Purchase #2	$207.89	11.484%	$231.7641	$231.76	$231.75	$231.80
Purchase #3	$90.79	7.732%	$97.8099	$97.81	$97.80	$97.80
Purchase #4	$241.35	3.651%	$250.1617	$250.16	$250.15	$250.20
Purchase #5	$77.86	9.723%	$85.4303	$85.43	$85.45	$85.40
Purchase #6	$66.77	6.478%	$71.0954	$71.10	$71.10	$71.10
Purchase #7	$6.95	6.151%	$7.3775	$7.38	$7.40	$7.40
7 purchase totals =	$909.87		$969.4572	$969.46	$969.45	$969.50