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	$83.62	10.330%	$92.2579	$92.26	$92.25	$92.30
Purchase #2	$131.27	4.540%	$137.2297	$137.23	$137.25	$137.20
Purchase #3	$236.70	11.818%	$264.6732	$264.67	$264.65	$264.70
Purchase #4	$173.39	7.766%	$186.8555	$186.86	$186.85	$186.90
Purchase #5	$66.70	6.485%	$71.0255	$71.03	$71.05	$71.00
Purchase #6	$67.71	6.387%	$72.0346	$72.03	$72.05	$72.00
Purchase #7	$237.47	10.296%	$261.9199	$261.92	$261.90	$261.90
7 purchase totals =	$996.86		$1,085.9963	$1,086.00	$1,086.00	$1,086.00