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	$82.95	7.656%	$89.3007	$89.30	$89.30	$89.30
Purchase #2	$135.79	5.578%	$143.3644	$143.36	$143.35	$143.40
Purchase #3	$234.47	13.477%	$266.0695	$266.07	$266.05	$266.10
Purchase #4	$201.73	10.612%	$223.1376	$223.14	$223.15	$223.10
Purchase #5	$164.71	3.401%	$170.3118	$170.31	$170.30	$170.30
Purchase #6	$141.65	6.409%	$150.7283	$150.73	$150.75	$150.70
Purchase #7	$91.30	7.450%	$98.1019	$98.10	$98.10	$98.10
7 purchase totals =	$1,052.60		$1,141.0142	$1,141.01	$1,141.00	$1,141.00