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	$32.38	8.124%	$35.0106	$35.01	$35.00	$35.00
Purchase #2	$138.30	8.579%	$150.1648	$150.16	$150.15	$150.20
Purchase #3	$85.61	13.160%	$96.8763	$96.88	$96.90	$96.90
Purchase #4	$178.50	11.838%	$199.6308	$199.63	$199.65	$199.60
Purchase #5	$39.76	6.564%	$42.3698	$42.37	$42.35	$42.40
Purchase #6	$226.47	5.764%	$239.5237	$239.52	$239.50	$239.50
Purchase #7	$132.29	10.335%	$145.9622	$145.96	$145.95	$146.00
7 purchase totals =	$833.31		$909.5382	$909.53	$909.50	$909.60