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	$248.29	13.836%	$282.6434	$282.64	$282.65	$282.60
Purchase #2	$81.54	11.352%	$90.7964	$90.80	$90.80	$90.80
Purchase #3	$153.57	13.842%	$174.8272	$174.83	$174.85	$174.80
Purchase #4	$225.27	11.327%	$250.7863	$250.79	$250.80	$250.80
Purchase #5	$36.36	3.121%	$37.4948	$37.49	$37.50	$37.50
Purchase #6	$189.60	3.102%	$195.4814	$195.48	$195.50	$195.50
Purchase #7	$19.54	4.655%	$20.4496	$20.45	$20.45	$20.40
7 purchase totals =	$954.17		$1,052.4791	$1,052.48	$1,052.55	$1,052.40