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	$115.67	6.775%	$123.5066	$123.51	$123.50	$123.50
Purchase #2	$35.77	5.304%	$37.6672	$37.67	$37.65	$37.70
Purchase #3	$69.26	10.616%	$76.6126	$76.61	$76.60	$76.60
Purchase #4	$11.73	5.127%	$12.3314	$12.33	$12.35	$12.30
Purchase #5	$151.88	3.419%	$157.0728	$157.07	$157.05	$157.10
Purchase #6	$115.60	7.280%	$124.0157	$124.02	$124.00	$124.00
Purchase #7	$74.60	5.732%	$78.8761	$78.88	$78.90	$78.90
7 purchase totals =	$574.51		$610.0824	$610.09	$610.05	$610.10