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	$226.54	11.832%	$253.3442	$253.34	$253.35	$253.30
Purchase #2	$93.31	7.270%	$100.0936	$100.09	$100.10	$100.10
Purchase #3	$88.75	10.116%	$97.728	$97.73	$97.75	$97.70
Purchase #4	$177.89	10.385%	$196.3639	$196.36	$196.35	$196.40
Purchase #5	$109.79	7.830%	$118.3866	$118.39	$118.40	$118.40
Purchase #6	$247.41	7.429%	$265.7901	$265.79	$265.80	$265.80
Purchase #7	$207.73	5.345%	$218.8332	$218.83	$218.85	$218.80
7 purchase totals =	$1,151.42		$1,250.5396	$1,250.53	$1,250.60	$1,250.50