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	$105.44	13.191%	$119.3486	$119.35	$119.35	$119.30
Purchase #2	$145.54	11.532%	$162.3237	$162.32	$162.30	$162.30
Purchase #3	$97.49	5.589%	$102.9387	$102.94	$102.95	$102.90
Purchase #4	$139.32	13.576%	$158.2341	$158.23	$158.25	$158.20
Purchase #5	$180.73	8.186%	$195.5246	$195.52	$195.50	$195.50
Purchase #6	$238.76	11.732%	$266.7713	$266.77	$266.75	$266.80
Purchase #7	$83.57	6.595%	$89.0814	$89.08	$89.10	$89.10
7 purchase totals =	$990.85		$1,094.2224	$1,094.21	$1,094.20	$1,094.10