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	$111.94	10.474%	$123.6646	$123.66	$123.65	$123.70
Purchase #2	$210.65	5.592%	$222.4295	$222.43	$222.45	$222.40
Purchase #3	$88.69	6.805%	$94.7254	$94.73	$94.75	$94.70
Purchase #4	$86.57	3.256%	$89.3887	$89.39	$89.40	$89.40
Purchase #5	$159.96	9.309%	$174.8507	$174.85	$174.85	$174.90
Purchase #6	$17.96	4.206%	$18.7154	$18.72	$18.70	$18.70
Purchase #7	$80.76	6.697%	$86.1685	$86.17	$86.15	$86.20
7 purchase totals =	$756.53		$809.9428	$809.95	$809.95	$810.00