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	$139.64	8.861%	$152.0135	$152.01	$152.00	$152.00
Purchase #2	$54.93	13.335%	$62.2549	$62.25	$62.25	$62.30
Purchase #3	$183.69	5.857%	$194.4487	$194.45	$194.45	$194.40
Purchase #4	$212.92	4.679%	$222.8825	$222.88	$222.90	$222.90
Purchase #5	$85.43	3.333%	$88.2774	$88.28	$88.30	$88.30
Purchase #6	$80.66	12.169%	$90.4755	$90.48	$90.50	$90.50
Purchase #7	$179.93	7.232%	$192.9425	$192.94	$192.95	$192.90
7 purchase totals =	$937.20		$1,003.2950	$1,003.29	$1,003.35	$1,003.30