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	$25.35	5.824%	$26.8264	$26.83	$26.85	$26.80
Purchase #2	$185.59	13.471%	$210.5908	$210.59	$210.60	$210.60
Purchase #3	$218.88	13.840%	$249.173	$249.17	$249.15	$249.20
Purchase #4	$242.97	12.659%	$273.7276	$273.73	$273.75	$273.70
Purchase #5	$179.85	5.307%	$189.3946	$189.39	$189.40	$189.40
Purchase #6	$18.72	9.653%	$20.527	$20.53	$20.55	$20.50
Purchase #7	$33.31	12.237%	$37.3861	$37.39	$37.40	$37.40
7 purchase totals =	$904.67		$1,007.6255	$1,007.63	$1,007.70	$1,007.60