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	$51.93	5.441%	$54.7555	$54.76	$54.75	$54.80
Purchase #2	$219.83	4.397%	$229.4959	$229.50	$229.50	$229.50
Purchase #3	$86.66	3.530%	$89.7191	$89.72	$89.70	$89.70
Purchase #4	$161.92	3.140%	$167.0043	$167.00	$167.00	$167.00
Purchase #5	$211.43	6.753%	$225.7079	$225.71	$225.70	$225.70
Purchase #6	$51.61	12.204%	$57.9085	$57.91	$57.90	$57.90
Purchase #7	$105.49	4.188%	$109.9079	$109.91	$109.90	$109.90
7 purchase totals =	$888.87		$934.4991	$934.51	$934.45	$934.50