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	$107.44	9.742%	$117.9068	$117.91	$117.90	$117.90
Purchase #2	$102.44	10.757%	$113.4595	$113.46	$113.45	$113.50
Purchase #3	$183.91	4.102%	$191.454	$191.45	$191.45	$191.50
Purchase #4	$46.85	3.273%	$48.3834	$48.38	$48.40	$48.40
Purchase #5	$220.89	13.585%	$250.8979	$250.90	$250.90	$250.90
Purchase #6	$111.53	5.692%	$117.8783	$117.88	$117.90	$117.90
Purchase #7	$190.44	4.303%	$198.6346	$198.63	$198.65	$198.60
7 purchase totals =	$963.50		$1,038.6145	$1,038.61	$1,038.65	$1,038.70