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	$106.93	3.836%	$111.0318	$111.03	$111.05	$111.00
Purchase #2	$187.37	12.369%	$210.5458	$210.55	$210.55	$210.50
Purchase #3	$115.93	9.146%	$126.533	$126.53	$126.55	$126.50
Purchase #4	$103.59	3.301%	$107.0095	$107.01	$107.00	$107.00
Purchase #5	$52.69	3.300%	$54.4288	$54.43	$54.45	$54.40
Purchase #6	$143.67	11.549%	$160.2624	$160.26	$160.25	$160.30
Purchase #7	$44.91	12.177%	$50.3787	$50.38	$50.40	$50.40
7 purchase totals =	$755.09		$820.1900	$820.19	$820.25	$820.10