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	$90.49	9.334%	$98.9363	$98.94	$98.95	$98.90
Purchase #2	$171.96	8.105%	$185.8974	$185.90	$185.90	$185.90
Purchase #3	$233.27	9.190%	$254.7075	$254.71	$254.70	$254.70
Purchase #4	$37.31	4.849%	$39.1192	$39.12	$39.10	$39.10
Purchase #5	$169.84	3.814%	$176.3177	$176.32	$176.30	$176.30
Purchase #6	$203.61	6.500%	$216.8447	$216.84	$216.85	$216.80
Purchase #7	$57.50	9.314%	$62.8556	$62.86	$62.85	$62.90
7 purchase totals =	$963.98		$1,034.6784	$1,034.69	$1,034.65	$1,034.60