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	$250.95	7.365%	$269.4325	$269.43	$269.45	$269.40
Purchase #2	$42.91	3.236%	$44.2986	$44.30	$44.30	$44.30
Purchase #3	$220.58	13.155%	$249.5973	$249.60	$249.60	$249.60
Purchase #4	$67.46	8.526%	$73.2116	$73.21	$73.20	$73.20
Purchase #5	$28.42	4.160%	$29.6023	$29.60	$29.60	$29.60
Purchase #6	$141.97	4.846%	$148.8499	$148.85	$148.85	$148.80
Purchase #7	$191.47	3.727%	$198.6061	$198.61	$198.60	$198.60
7 purchase totals =	$943.76		$1,013.5983	$1,013.60	$1,013.60	$1,013.50