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	$123.91	7.270%	$132.9183	$132.92	$132.90	$132.90
Purchase #2	$119.44	9.751%	$131.0866	$131.09	$131.10	$131.10
Purchase #3	$216.28	11.869%	$241.9503	$241.95	$241.95	$242.00
Purchase #4	$150.77	11.151%	$167.5824	$167.58	$167.60	$167.60
Purchase #5	$131.98	12.584%	$148.5884	$148.59	$148.60	$148.60
Purchase #6	$42.31	5.245%	$44.5292	$44.53	$44.55	$44.50
Purchase #7	$245.86	3.840%	$255.301	$255.30	$255.30	$255.30
7 purchase totals =	$1,030.55		$1,121.9562	$1,121.96	$1,122.00	$1,122.00