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	$82.26	5.538%	$86.8156	$86.82	$86.80	$86.80
Purchase #2	$244.89	10.332%	$270.192	$270.19	$270.20	$270.20
Purchase #3	$134.79	8.786%	$146.6326	$146.63	$146.65	$146.60
Purchase #4	$142.70	5.778%	$150.9452	$150.95	$150.95	$150.90
Purchase #5	$111.41	10.511%	$123.1203	$123.12	$123.10	$123.10
Purchase #6	$67.99	13.320%	$77.0463	$77.05	$77.05	$77.00
Purchase #7	$141.74	13.794%	$161.2916	$161.29	$161.30	$161.30
7 purchase totals =	$925.78		$1,016.0436	$1,016.05	$1,016.05	$1,015.90