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	$153.69	11.530%	$171.4105	$171.41	$171.40	$171.40
Purchase #2	$22.27	11.801%	$24.8981	$24.90	$24.90	$24.90
Purchase #3	$55.97	6.195%	$59.4373	$59.44	$59.45	$59.40
Purchase #4	$20.53	9.462%	$22.4725	$22.47	$22.45	$22.50
Purchase #5	$68.38	5.679%	$72.2633	$72.26	$72.25	$72.30
Purchase #6	$79.83	4.160%	$83.1509	$83.15	$83.15	$83.20
Purchase #7	$219.75	11.186%	$244.3312	$244.33	$244.35	$244.30
7 purchase totals =	$620.42		$677.9638	$677.96	$677.95	$678.00