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	$231.54	6.296%	$246.1178	$246.12	$246.10	$246.10
Purchase #2	$94.38	10.826%	$104.5976	$104.60	$104.60	$104.60
Purchase #3	$41.42	5.836%	$43.8373	$43.84	$43.85	$43.80
Purchase #4	$101.29	7.743%	$109.1329	$109.13	$109.15	$109.10
Purchase #5	$37.27	10.282%	$41.1021	$41.10	$41.10	$41.10
Purchase #6	$205.31	10.706%	$227.2905	$227.29	$227.30	$227.30
Purchase #7	$229.73	6.723%	$245.1747	$245.17	$245.15	$245.20
7 purchase totals =	$940.94		$1,017.2529	$1,017.25	$1,017.25	$1,017.20