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	$224.26	9.591%	$245.7688	$245.77	$245.75	$245.80
Purchase #2	$196.86	4.733%	$206.1774	$206.18	$206.20	$206.20
Purchase #3	$100.59	11.543%	$112.2011	$112.20	$112.20	$112.20
Purchase #4	$80.26	7.815%	$86.5323	$86.53	$86.55	$86.50
Purchase #5	$90.34	11.203%	$100.4608	$100.46	$100.45	$100.50
Purchase #6	$64.89	13.626%	$73.7319	$73.73	$73.75	$73.70
Purchase #7	$233.56	9.430%	$255.5847	$255.58	$255.60	$255.60
7 purchase totals =	$990.76		$1,080.4570	$1,080.45	$1,080.50	$1,080.50