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	$191.65	6.485%	$204.0785	$204.08	$204.10	$204.10
Purchase #2	$223.37	7.680%	$240.5248	$240.52	$240.50	$240.50
Purchase #3	$91.34	7.836%	$98.4974	$98.50	$98.50	$98.50
Purchase #4	$157.61	11.325%	$175.4593	$175.46	$175.45	$175.50
Purchase #5	$168.60	6.338%	$179.2859	$179.29	$179.30	$179.30
Purchase #6	$84.88	10.411%	$93.7169	$93.72	$93.70	$93.70
Purchase #7	$114.60	11.150%	$127.3779	$127.38	$127.40	$127.40
7 purchase totals =	$1,032.05		$1,118.9407	$1,118.95	$1,118.95	$1,119.00