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	$83.51	3.228%	$86.2057	$86.21	$86.20	$86.20
Purchase #2	$80.49	9.766%	$88.3507	$88.35	$88.35	$88.40
Purchase #3	$196.78	8.541%	$213.587	$213.59	$213.60	$213.60
Purchase #4	$48.75	3.325%	$50.3709	$50.37	$50.35	$50.40
Purchase #5	$146.80	6.778%	$156.7501	$156.75	$156.75	$156.80
Purchase #6	$179.87	6.345%	$191.2828	$191.28	$191.30	$191.30
Purchase #7	$70.65	11.623%	$78.8616	$78.86	$78.85	$78.90
7 purchase totals =	$806.85		$865.4088	$865.41	$865.40	$865.60