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	$171.54	9.344%	$187.5687	$187.57	$187.55	$187.60
Purchase #2	$174.88	5.440%	$184.3935	$184.39	$184.40	$184.40
Purchase #3	$31.80	12.457%	$35.7613	$35.76	$35.75	$35.80
Purchase #4	$87.61	3.807%	$90.9453	$90.95	$90.95	$90.90
Purchase #5	$69.73	11.796%	$77.9554	$77.96	$77.95	$78.00
Purchase #6	$24.51	12.186%	$27.4968	$27.50	$27.50	$27.50
Purchase #7	$72.72	5.539%	$76.748	$76.75	$76.75	$76.70
7 purchase totals =	$632.79		$680.8690	$680.88	$680.85	$680.90