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	$184.81	8.145%	$199.8628	$199.86	$199.85	$199.90
Purchase #2	$189.28	8.242%	$204.8805	$204.88	$204.90	$204.90
Purchase #3	$220.31	6.614%	$234.8813	$234.88	$234.90	$234.90
Purchase #4	$48.81	5.492%	$51.4906	$51.49	$51.50	$51.50
Purchase #5	$77.84	10.638%	$86.1206	$86.12	$86.10	$86.10
Purchase #6	$78.83	5.417%	$83.1002	$83.10	$83.10	$83.10
Purchase #7	$99.47	11.852%	$111.2592	$111.26	$111.25	$111.30
7 purchase totals =	$899.35		$971.5952	$971.59	$971.60	$971.70