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	$168.88	12.581%	$190.1268	$190.13	$190.15	$190.10
Purchase #2	$93.83	10.251%	$103.4485	$103.45	$103.45	$103.40
Purchase #3	$215.81	6.194%	$229.1773	$229.18	$229.20	$229.20
Purchase #4	$109.51	10.328%	$120.8202	$120.82	$120.80	$120.80
Purchase #5	$86.28	10.868%	$95.6569	$95.66	$95.65	$95.70
Purchase #6	$6.71	10.636%	$7.4237	$7.42	$7.40	$7.40
Purchase #7	$49.47	6.230%	$52.552	$52.55	$52.55	$52.60
7 purchase totals =	$730.49		$799.2054	$799.21	$799.20	$799.20