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	$221.26	8.607%	$240.3038	$240.30	$240.30	$240.30
Purchase #2	$127.37	11.767%	$142.3576	$142.36	$142.35	$142.40
Purchase #3	$184.41	10.174%	$203.1719	$203.17	$203.15	$203.20
Purchase #4	$187.59	11.661%	$209.4649	$209.46	$209.45	$209.50
Purchase #5	$92.69	11.262%	$103.1287	$103.13	$103.15	$103.10
Purchase #6	$43.97	3.705%	$45.5991	$45.60	$45.60	$45.60
Purchase #7	$116.26	4.342%	$121.308	$121.31	$121.30	$121.30
7 purchase totals =	$973.55		$1,065.3340	$1,065.33	$1,065.30	$1,065.40