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	$124.87	5.775%	$132.0812	$132.08	$132.10	$132.10
Purchase #2	$59.46	10.305%	$65.5874	$65.59	$65.60	$65.60
Purchase #3	$175.68	3.770%	$182.3031	$182.30	$182.30	$182.30
Purchase #4	$177.73	4.590%	$185.8878	$185.89	$185.90	$185.90
Purchase #5	$196.37	12.429%	$220.7768	$220.78	$220.80	$220.80
Purchase #6	$136.76	10.851%	$151.5998	$151.60	$151.60	$151.60
Purchase #7	$109.32	9.625%	$119.8421	$119.84	$119.85	$119.80
7 purchase totals =	$980.19		$1,058.0782	$1,058.08	$1,058.15	$1,058.10