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	$10.86	4.662%	$11.3663	$11.37	$11.35	$11.40
Purchase #2	$86.46	5.761%	$91.441	$91.44	$91.45	$91.40
Purchase #3	$90.85	8.180%	$98.2815	$98.28	$98.30	$98.30
Purchase #4	$144.50	5.825%	$152.9171	$152.92	$152.90	$152.90
Purchase #5	$91.57	5.152%	$96.2877	$96.29	$96.30	$96.30
Purchase #6	$26.84	3.373%	$27.7453	$27.75	$27.75	$27.70
Purchase #7	$30.94	7.139%	$33.1488	$33.15	$33.15	$33.10
7 purchase totals =	$482.02		$511.1877	$511.20	$511.20	$511.10