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	$203.57	6.545%	$216.8937	$216.89	$216.90	$216.90
Purchase #2	$145.40	8.215%	$157.3446	$157.34	$157.35	$157.30
Purchase #3	$44.33	8.305%	$48.0116	$48.01	$48.00	$48.00
Purchase #4	$198.84	9.333%	$217.3977	$217.40	$217.40	$217.40
Purchase #5	$160.98	10.666%	$178.1501	$178.15	$178.15	$178.20
Purchase #6	$83.33	6.861%	$89.0473	$89.05	$89.05	$89.00
Purchase #7	$96.51	9.490%	$105.6688	$105.67	$105.65	$105.70
7 purchase totals =	$932.96		$1,012.5138	$1,012.51	$1,012.50	$1,012.50