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	$237.91	11.138%	$264.4084	$264.41	$264.40	$264.40
Purchase #2	$83.83	3.673%	$86.9091	$86.91	$86.90	$86.90
Purchase #3	$65.62	10.440%	$72.4707	$72.47	$72.45	$72.50
Purchase #4	$56.58	3.311%	$58.4534	$58.45	$58.45	$58.50
Purchase #5	$177.89	9.675%	$195.1009	$195.10	$195.10	$195.10
Purchase #6	$88.96	13.339%	$100.8264	$100.83	$100.85	$100.80
Purchase #7	$151.57	3.477%	$156.8401	$156.84	$156.85	$156.80
7 purchase totals =	$862.36		$935.0090	$935.01	$935.00	$935.00