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	$47.29	3.379%	$48.8879	$48.89	$48.90	$48.90
Purchase #2	$157.59	13.531%	$178.9135	$178.91	$178.90	$178.90
Purchase #3	$80.76	6.342%	$85.8818	$85.88	$85.90	$85.90
Purchase #4	$157.77	6.551%	$168.1055	$168.11	$168.10	$168.10
Purchase #5	$215.66	8.637%	$234.2866	$234.29	$234.30	$234.30
Purchase #6	$182.70	12.637%	$205.7878	$205.79	$205.80	$205.80
Purchase #7	$90.87	10.806%	$100.6894	$100.69	$100.70	$100.70
7 purchase totals =	$932.64		$1,022.5525	$1,022.56	$1,022.60	$1,022.60