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	$194.31	11.583%	$216.8169	$216.82	$216.80	$216.80
Purchase #2	$225.71	3.226%	$232.9914	$232.99	$233.00	$233.00
Purchase #3	$85.32	4.464%	$89.1287	$89.13	$89.15	$89.10
Purchase #4	$240.80	9.329%	$263.2642	$263.26	$263.25	$263.30
Purchase #5	$85.44	4.213%	$89.0396	$89.04	$89.05	$89.00
Purchase #6	$23.80	3.600%	$24.6568	$24.66	$24.65	$24.70
Purchase #7	$171.29	6.195%	$181.9014	$181.90	$181.90	$181.90
7 purchase totals =	$1,026.67		$1,097.7990	$1,097.80	$1,097.80	$1,097.80