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	$83.76	10.205%	$92.3077	$92.31	$92.30	$92.30
Purchase #2	$72.83	13.677%	$82.791	$82.79	$82.80	$82.80
Purchase #3	$104.50	11.142%	$116.1434	$116.14	$116.15	$116.10
Purchase #4	$36.95	10.623%	$40.8752	$40.88	$40.90	$40.90
Purchase #5	$163.33	9.819%	$179.3674	$179.37	$179.35	$179.40
Purchase #6	$74.47	9.579%	$81.6035	$81.60	$81.60	$81.60
Purchase #7	$20.92	4.764%	$21.9166	$21.92	$21.90	$21.90
7 purchase totals =	$556.76		$615.0048	$615.01	$615.00	$615.00