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	$230.41	4.807%	$241.4858	$241.49	$241.50	$241.50
Purchase #2	$143.46	12.446%	$161.315	$161.32	$161.30	$161.30
Purchase #3	$35.47	12.417%	$39.8743	$39.87	$39.85	$39.90
Purchase #4	$191.39	10.805%	$212.0697	$212.07	$212.05	$212.10
Purchase #5	$85.96	5.483%	$90.6732	$90.67	$90.65	$90.70
Purchase #6	$212.36	6.396%	$225.9425	$225.94	$225.95	$225.90
Purchase #7	$34.68	10.181%	$38.2108	$38.21	$38.20	$38.20
7 purchase totals =	$933.73		$1,009.5713	$1,009.57	$1,009.50	$1,009.60