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	$165.49	5.475%	$174.5506	$174.55	$174.55	$174.60
Purchase #2	$54.66	9.724%	$59.9751	$59.98	$60.00	$60.00
Purchase #3	$223.76	13.277%	$253.4686	$253.47	$253.45	$253.50
Purchase #4	$37.80	11.344%	$42.088	$42.09	$42.10	$42.10
Purchase #5	$41.82	10.179%	$46.0769	$46.08	$46.10	$46.10
Purchase #6	$98.89	10.401%	$109.1755	$109.18	$109.20	$109.20
Purchase #7	$150.35	7.605%	$161.7841	$161.78	$161.80	$161.80
7 purchase totals =	$772.77		$847.1188	$847.13	$847.20	$847.30