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	$116.52	12.529%	$131.1188	$131.12	$131.10	$131.10
Purchase #2	$153.81	11.231%	$171.0844	$171.08	$171.10	$171.10
Purchase #3	$142.87	13.701%	$162.4446	$162.44	$162.45	$162.40
Purchase #4	$26.93	6.115%	$28.5768	$28.58	$28.60	$28.60
Purchase #5	$13.47	3.327%	$13.9181	$13.92	$13.90	$13.90
Purchase #6	$28.41	9.614%	$31.1413	$31.14	$31.15	$31.10
Purchase #7	$84.26	11.843%	$94.2389	$94.24	$94.25	$94.20
7 purchase totals =	$566.27		$632.5229	$632.52	$632.55	$632.40