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	$94.35	4.412%	$98.5127	$98.51	$98.50	$98.50
Purchase #2	$95.70	4.582%	$100.085	$100.09	$100.10	$100.10
Purchase #3	$65.43	13.840%	$74.4855	$74.49	$74.50	$74.50
Purchase #4	$142.75	12.148%	$160.0913	$160.09	$160.10	$160.10
Purchase #5	$198.37	8.401%	$215.0351	$215.04	$215.05	$215.00
Purchase #6	$48.61	12.456%	$54.6649	$54.66	$54.65	$54.70
Purchase #7	$137.90	9.154%	$150.5234	$150.52	$150.50	$150.50
7 purchase totals =	$783.11		$853.3979	$853.40	$853.40	$853.40