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	$219.96	12.455%	$247.356	$247.36	$247.35	$247.40
Purchase #2	$14.89	4.200%	$15.5154	$15.52	$15.50	$15.50
Purchase #3	$152.46	7.808%	$164.3641	$164.36	$164.35	$164.40
Purchase #4	$243.59	8.563%	$264.4486	$264.45	$264.45	$264.40
Purchase #5	$162.95	9.554%	$178.5182	$178.52	$178.50	$178.50
Purchase #6	$99.85	6.872%	$106.7117	$106.71	$106.70	$106.70
Purchase #7	$169.53	10.392%	$187.1476	$187.15	$187.15	$187.10
7 purchase totals =	$1,063.23		$1,164.0616	$1,164.07	$1,164.00	$1,164.00