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	$20.38	7.663%	$21.9417	$21.94	$21.95	$21.90
Purchase #2	$131.53	10.693%	$145.5945	$145.59	$145.60	$145.60
Purchase #3	$147.54	6.336%	$156.8881	$156.89	$156.90	$156.90
Purchase #4	$232.44	4.793%	$243.5808	$243.58	$243.60	$243.60
Purchase #5	$142.36	9.772%	$156.2714	$156.27	$156.25	$156.30
Purchase #6	$18.74	10.626%	$20.7313	$20.73	$20.75	$20.70
Purchase #7	$137.27	12.478%	$154.3986	$154.40	$154.40	$154.40
7 purchase totals =	$830.26		$899.4064	$899.40	$899.45	$899.40