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	$132.63	12.795%	$149.6	$149.60	$149.60	$149.60
Purchase #2	$80.56	8.598%	$87.4865	$87.49	$87.50	$87.50
Purchase #3	$92.44	9.870%	$101.5638	$101.56	$101.55	$101.60
Purchase #4	$238.90	10.839%	$264.7944	$264.79	$264.80	$264.80
Purchase #5	$142.29	5.731%	$150.4446	$150.44	$150.45	$150.40
Purchase #6	$38.88	8.803%	$42.3026	$42.30	$42.30	$42.30
Purchase #7	$206.40	6.579%	$219.9791	$219.98	$220.00	$220.00
7 purchase totals =	$932.10		$1,016.1710	$1,016.16	$1,016.20	$1,016.20