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	$161.89	12.633%	$182.3416	$182.34	$182.35	$182.30
Purchase #2	$177.56	6.154%	$188.487	$188.49	$188.50	$188.50
Purchase #3	$215.80	5.261%	$227.1532	$227.15	$227.15	$227.20
Purchase #4	$213.33	10.574%	$235.8875	$235.89	$235.90	$235.90
Purchase #5	$196.54	11.874%	$219.8772	$219.88	$219.90	$219.90
Purchase #6	$69.74	4.233%	$72.6921	$72.69	$72.70	$72.70
Purchase #7	$11.25	13.144%	$12.7287	$12.73	$12.75	$12.70
7 purchase totals =	$1,046.11		$1,139.1673	$1,139.17	$1,139.25	$1,139.20