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	$181.94	9.163%	$198.6112	$198.61	$198.60	$198.60
Purchase #2	$104.50	6.472%	$111.2632	$111.26	$111.25	$111.30
Purchase #3	$18.52	6.205%	$19.6692	$19.67	$19.65	$19.70
Purchase #4	$231.59	6.166%	$245.8698	$245.87	$245.85	$245.90
Purchase #5	$219.32	12.205%	$246.088	$246.09	$246.10	$246.10
Purchase #6	$21.52	3.707%	$22.3177	$22.32	$22.30	$22.30
Purchase #7	$72.52	8.126%	$78.413	$78.41	$78.40	$78.40
7 purchase totals =	$849.91		$922.2321	$922.23	$922.15	$922.30