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	$149.88	12.507%	$168.6255	$168.63	$168.65	$168.60
Purchase #2	$118.75	10.262%	$130.9361	$130.94	$130.95	$130.90
Purchase #3	$162.70	4.861%	$170.6088	$170.61	$170.60	$170.60
Purchase #4	$177.41	7.474%	$190.6696	$190.67	$190.65	$190.70
Purchase #5	$148.94	6.452%	$158.5496	$158.55	$158.55	$158.50
Purchase #6	$200.71	11.408%	$223.607	$223.61	$223.60	$223.60
Purchase #7	$112.30	6.248%	$119.3165	$119.32	$119.30	$119.30
7 purchase totals =	$1,070.69		$1,162.3131	$1,162.33	$1,162.30	$1,162.20