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	$144.50	8.556%	$156.8634	$156.86	$156.85	$156.90
Purchase #2	$211.32	12.763%	$238.2908	$238.29	$238.30	$238.30
Purchase #3	$116.70	11.661%	$130.3084	$130.31	$130.30	$130.30
Purchase #4	$157.27	7.484%	$169.0401	$169.04	$169.05	$169.00
Purchase #5	$190.50	8.159%	$206.0429	$206.04	$206.05	$206.00
Purchase #6	$138.28	6.201%	$146.8547	$146.85	$146.85	$146.90
Purchase #7	$65.39	9.334%	$71.4935	$71.49	$71.50	$71.50
7 purchase totals =	$1,023.96		$1,118.8938	$1,118.88	$1,118.90	$1,118.90