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	$109.59	12.407%	$123.1868	$123.19	$123.20	$123.20
Purchase #2	$171.43	7.701%	$184.6318	$184.63	$184.65	$184.60
Purchase #3	$69.69	12.294%	$78.2577	$78.26	$78.25	$78.30
Purchase #4	$245.71	7.731%	$264.7058	$264.71	$264.70	$264.70
Purchase #5	$131.90	13.659%	$149.9162	$149.92	$149.90	$149.90
Purchase #6	$87.51	5.316%	$92.162	$92.16	$92.15	$92.20
Purchase #7	$164.61	7.261%	$176.5623	$176.56	$176.55	$176.60
7 purchase totals =	$980.44		$1,069.4226	$1,069.43	$1,069.40	$1,069.50