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	$105.84	11.423%	$117.9301	$117.93	$117.95	$117.90
Purchase #2	$55.85	7.654%	$60.1248	$60.12	$60.10	$60.10
Purchase #3	$188.26	4.247%	$196.2554	$196.26	$196.25	$196.30
Purchase #4	$224.67	10.552%	$248.3772	$248.38	$248.40	$248.40
Purchase #5	$241.99	6.833%	$258.5252	$258.53	$258.55	$258.50
Purchase #6	$70.83	13.284%	$80.2391	$80.24	$80.25	$80.20
Purchase #7	$95.73	5.214%	$100.7214	$100.72	$100.70	$100.70
7 purchase totals =	$983.17		$1,062.1732	$1,062.18	$1,062.20	$1,062.10