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	$139.99	9.870%	$153.807	$153.81	$153.80	$153.80
Purchase #2	$75.90	8.752%	$82.5428	$82.54	$82.55	$82.50
Purchase #3	$65.87	9.132%	$71.8852	$71.89	$71.90	$71.90
Purchase #4	$136.85	6.428%	$145.6467	$145.65	$145.65	$145.60
Purchase #5	$212.29	5.402%	$223.7579	$223.76	$223.75	$223.80
Purchase #6	$228.34	5.555%	$241.0243	$241.02	$241.00	$241.00
Purchase #7	$92.85	13.636%	$105.511	$105.51	$105.50	$105.50
7 purchase totals =	$952.09		$1,024.1749	$1,024.18	$1,024.15	$1,024.10