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	$228.85	6.558%	$243.858	$243.86	$243.85	$243.90
Purchase #2	$127.90	6.728%	$136.5051	$136.51	$136.50	$136.50
Purchase #3	$215.69	9.112%	$235.3437	$235.34	$235.35	$235.30
Purchase #4	$64.76	11.500%	$72.2074	$72.21	$72.20	$72.20
Purchase #5	$68.81	12.137%	$77.1615	$77.16	$77.15	$77.20
Purchase #6	$41.61	9.359%	$45.5043	$45.50	$45.50	$45.50
Purchase #7	$49.30	10.638%	$54.5445	$54.54	$54.55	$54.50
7 purchase totals =	$796.92		$865.1245	$865.12	$865.10	$865.10