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	$179.38	9.388%	$196.2202	$196.22	$196.20	$196.20
Purchase #2	$223.91	7.414%	$240.5107	$240.51	$240.50	$240.50
Purchase #3	$63.86	10.522%	$70.5793	$70.58	$70.60	$70.60
Purchase #4	$7.42	6.349%	$7.8911	$7.89	$7.90	$7.90
Purchase #5	$126.37	11.253%	$140.5904	$140.59	$140.60	$140.60
Purchase #6	$200.32	12.169%	$224.6969	$224.70	$224.70	$224.70
Purchase #7	$53.59	11.416%	$59.7078	$59.71	$59.70	$59.70
7 purchase totals =	$854.85		$940.1964	$940.20	$940.20	$940.20