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	$123.43	13.801%	$140.4646	$140.46	$140.45	$140.50
Purchase #2	$221.85	5.600%	$234.2736	$234.27	$234.25	$234.30
Purchase #3	$29.92	10.719%	$33.1271	$33.13	$33.15	$33.10
Purchase #4	$220.74	3.446%	$228.3467	$228.35	$228.35	$228.30
Purchase #5	$81.42	11.528%	$90.8061	$90.81	$90.80	$90.80
Purchase #6	$88.77	13.154%	$100.4468	$100.45	$100.45	$100.40
Purchase #7	$216.66	11.813%	$242.254	$242.25	$242.25	$242.30
7 purchase totals =	$982.79		$1,069.7189	$1,069.72	$1,069.70	$1,069.70