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	$106.62	7.357%	$114.464	$114.46	$114.45	$114.50
Purchase #2	$201.44	10.191%	$221.9688	$221.97	$221.95	$222.00
Purchase #3	$49.98	4.683%	$52.3206	$52.32	$52.30	$52.30
Purchase #4	$101.28	3.737%	$105.0648	$105.06	$105.05	$105.10
Purchase #5	$57.51	3.434%	$59.4849	$59.48	$59.50	$59.50
Purchase #6	$145.43	11.620%	$162.329	$162.33	$162.35	$162.30
Purchase #7	$187.51	5.211%	$197.2811	$197.28	$197.30	$197.30
7 purchase totals =	$849.77		$912.9132	$912.90	$912.90	$913.00