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	$198.70	5.441%	$209.5113	$209.51	$209.50	$209.50
Purchase #2	$134.78	13.253%	$152.6424	$152.64	$152.65	$152.60
Purchase #3	$9.82	8.850%	$10.6891	$10.69	$10.70	$10.70
Purchase #4	$39.34	4.209%	$40.9958	$41.00	$41.00	$41.00
Purchase #5	$152.32	4.560%	$159.2658	$159.27	$159.25	$159.30
Purchase #6	$106.31	4.374%	$110.96	$110.96	$110.95	$111.00
Purchase #7	$228.28	12.248%	$256.2397	$256.24	$256.25	$256.20
7 purchase totals =	$869.55		$940.3041	$940.31	$940.30	$940.30