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	$184.87	6.483%	$196.8551	$196.86	$196.85	$196.90
Purchase #2	$18.47	12.843%	$20.8421	$20.84	$20.85	$20.80
Purchase #3	$85.31	9.771%	$93.6456	$93.65	$93.65	$93.60
Purchase #4	$5.99	9.722%	$6.5723	$6.57	$6.55	$6.60
Purchase #5	$92.29	4.177%	$96.145	$96.15	$96.15	$96.10
Purchase #6	$211.51	5.161%	$222.426	$222.43	$222.45	$222.40
Purchase #7	$149.52	8.493%	$162.2187	$162.22	$162.20	$162.20
7 purchase totals =	$747.96		$798.7048	$798.72	$798.70	$798.60