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	$155.96	11.458%	$173.8299	$173.83	$173.85	$173.80
Purchase #2	$210.46	6.661%	$224.4787	$224.48	$224.50	$224.50
Purchase #3	$103.39	7.452%	$111.0946	$111.09	$111.10	$111.10
Purchase #4	$64.59	4.243%	$67.3306	$67.33	$67.35	$67.30
Purchase #5	$9.56	5.150%	$10.0523	$10.05	$10.05	$10.10
Purchase #6	$39.92	11.537%	$44.5256	$44.53	$44.55	$44.50
Purchase #7	$123.61	9.460%	$135.3035	$135.30	$135.30	$135.30
7 purchase totals =	$707.49		$766.6152	$766.61	$766.70	$766.60