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	$41.78	4.346%	$43.5958	$43.60	$43.60	$43.60
Purchase #2	$90.81	5.145%	$95.4822	$95.48	$95.50	$95.50
Purchase #3	$222.33	11.119%	$247.0509	$247.05	$247.05	$247.10
Purchase #4	$250.34	5.842%	$264.9649	$264.96	$264.95	$265.00
Purchase #5	$60.57	7.842%	$65.3199	$65.32	$65.30	$65.30
Purchase #6	$129.32	6.400%	$137.5965	$137.60	$137.60	$137.60
Purchase #7	$23.89	10.801%	$26.4704	$26.47	$26.45	$26.50
7 purchase totals =	$819.04		$880.4806	$880.48	$880.45	$880.60