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	$13.95	10.841%	$15.4623	$15.46	$15.45	$15.50
Purchase #2	$162.79	10.271%	$179.5102	$179.51	$179.50	$179.50
Purchase #3	$85.67	5.771%	$90.614	$90.61	$90.60	$90.60
Purchase #4	$104.44	12.428%	$117.4198	$117.42	$117.40	$117.40
Purchase #5	$200.80	7.334%	$215.5267	$215.53	$215.55	$215.50
Purchase #6	$173.60	4.116%	$180.7454	$180.75	$180.75	$180.70
Purchase #7	$246.70	12.764%	$278.1888	$278.19	$278.20	$278.20
7 purchase totals =	$987.95		$1,077.4672	$1,077.47	$1,077.45	$1,077.40