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	$225.26	13.235%	$255.0732	$255.07	$255.05	$255.10
Purchase #2	$168.57	6.290%	$179.1731	$179.17	$179.15	$179.20
Purchase #3	$76.44	4.570%	$79.9333	$79.93	$79.95	$79.90
Purchase #4	$123.60	11.285%	$137.5483	$137.55	$137.55	$137.50
Purchase #5	$23.30	8.769%	$25.3432	$25.34	$25.35	$25.30
Purchase #6	$164.35	4.253%	$171.3398	$171.34	$171.35	$171.30
Purchase #7	$150.26	10.212%	$165.6046	$165.60	$165.60	$165.60
7 purchase totals =	$931.78		$1,014.0155	$1,014.00	$1,014.00	$1,013.90