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	$196.89	12.814%	$222.1195	$222.12	$222.10	$222.10
Purchase #2	$199.61	12.433%	$224.4275	$224.43	$224.45	$224.40
Purchase #3	$56.33	12.250%	$63.2304	$63.23	$63.25	$63.20
Purchase #4	$16.73	13.805%	$19.0396	$19.04	$19.05	$19.00
Purchase #5	$16.82	11.195%	$18.703	$18.70	$18.70	$18.70
Purchase #6	$111.58	13.353%	$126.4793	$126.48	$126.50	$126.50
Purchase #7	$151.73	6.806%	$162.0567	$162.06	$162.05	$162.10
7 purchase totals =	$749.69		$836.0560	$836.06	$836.10	$836.00