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	$207.81	4.689%	$217.5542	$217.55	$217.55	$217.60
Purchase #2	$116.28	6.175%	$123.4603	$123.46	$123.45	$123.50
Purchase #3	$59.63	13.549%	$67.7093	$67.71	$67.70	$67.70
Purchase #4	$166.95	12.756%	$188.2461	$188.25	$188.25	$188.20
Purchase #5	$59.73	4.742%	$62.5624	$62.56	$62.55	$62.60
Purchase #6	$17.29	7.540%	$18.5937	$18.59	$18.60	$18.60
Purchase #7	$157.66	5.681%	$166.6167	$166.62	$166.60	$166.60
7 purchase totals =	$785.35		$844.7427	$844.74	$844.70	$844.80