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	$121.72	10.455%	$134.4458	$134.45	$134.45	$134.40
Purchase #2	$40.62	11.655%	$45.3543	$45.35	$45.35	$45.40
Purchase #3	$54.85	11.583%	$61.2033	$61.20	$61.20	$61.20
Purchase #4	$137.82	13.428%	$156.3265	$156.33	$156.35	$156.30
Purchase #5	$217.37	13.572%	$246.8715	$246.87	$246.85	$246.90
Purchase #6	$81.40	11.765%	$90.9767	$90.98	$91.00	$91.00
Purchase #7	$69.76	11.862%	$78.0349	$78.03	$78.05	$78.00
7 purchase totals =	$723.54		$813.2130	$813.21	$813.25	$813.20