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	$234.86	4.483%	$245.3888	$245.39	$245.40	$245.40
Purchase #2	$25.73	5.370%	$27.1117	$27.11	$27.10	$27.10
Purchase #3	$231.31	12.193%	$259.5136	$259.51	$259.50	$259.50
Purchase #4	$6.37	8.710%	$6.9248	$6.92	$6.90	$6.90
Purchase #5	$94.32	11.377%	$105.0508	$105.05	$105.05	$105.10
Purchase #6	$135.48	8.627%	$147.1679	$147.17	$147.15	$147.20
Purchase #7	$242.27	5.292%	$255.0909	$255.09	$255.10	$255.10
7 purchase totals =	$970.34		$1,046.2485	$1,046.24	$1,046.20	$1,046.30