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	$148.53	5.366%	$156.5001	$156.50	$156.50	$156.50
Purchase #2	$226.50	9.107%	$247.1274	$247.13	$247.15	$247.10
Purchase #3	$223.85	13.786%	$254.71	$254.71	$254.70	$254.70
Purchase #4	$139.59	8.443%	$151.3756	$151.38	$151.40	$151.40
Purchase #5	$44.49	3.136%	$45.8852	$45.89	$45.90	$45.90
Purchase #6	$249.85	7.716%	$269.1284	$269.13	$269.15	$269.10
Purchase #7	$123.59	5.791%	$130.7471	$130.75	$130.75	$130.70
7 purchase totals =	$1,156.40		$1,255.4738	$1,255.49	$1,255.55	$1,255.40