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	$57.34	3.864%	$59.5556	$59.56	$59.55	$59.60
Purchase #2	$228.76	9.426%	$250.3229	$250.32	$250.30	$250.30
Purchase #3	$39.34	9.773%	$43.1847	$43.18	$43.20	$43.20
Purchase #4	$63.94	12.145%	$71.7055	$71.71	$71.70	$71.70
Purchase #5	$121.65	8.395%	$131.8625	$131.86	$131.85	$131.90
Purchase #6	$36.70	3.343%	$37.9269	$37.93	$37.95	$37.90
Purchase #7	$138.53	8.821%	$150.7497	$150.75	$150.75	$150.70
7 purchase totals =	$686.26		$745.3078	$745.31	$745.30	$745.30