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	$128.44	3.144%	$132.4782	$132.48	$132.50	$132.50
Purchase #2	$187.52	9.521%	$205.3738	$205.37	$205.35	$205.40
Purchase #3	$209.56	4.368%	$218.7136	$218.71	$218.70	$218.70
Purchase #4	$38.74	9.620%	$42.4668	$42.47	$42.45	$42.50
Purchase #5	$161.31	11.144%	$179.2864	$179.29	$179.30	$179.30
Purchase #6	$149.28	4.800%	$156.4454	$156.45	$156.45	$156.40
Purchase #7	$67.62	13.490%	$76.7419	$76.74	$76.75	$76.70
7 purchase totals =	$942.47		$1,011.5061	$1,011.51	$1,011.50	$1,011.50