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	$64.90	3.774%	$67.3493	$67.35	$67.35	$67.30
Purchase #2	$151.74	6.273%	$161.2587	$161.26	$161.25	$161.30
Purchase #3	$216.45	3.463%	$223.9457	$223.95	$223.95	$223.90
Purchase #4	$95.29	8.271%	$103.1714	$103.17	$103.15	$103.20
Purchase #5	$27.94	10.507%	$30.8757	$30.88	$30.90	$30.90
Purchase #6	$77.90	11.152%	$86.5874	$86.59	$86.60	$86.60
Purchase #7	$137.41	11.504%	$153.2176	$153.22	$153.20	$153.20
7 purchase totals =	$771.63		$826.4058	$826.42	$826.40	$826.40