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	$86.50	13.535%	$98.2078	$98.21	$98.20	$98.20
Purchase #2	$176.59	11.489%	$196.8784	$196.88	$196.90	$196.90
Purchase #3	$141.85	11.439%	$158.0762	$158.08	$158.10	$158.10
Purchase #4	$143.26	5.315%	$150.8743	$150.87	$150.85	$150.90
Purchase #5	$80.69	6.672%	$86.0736	$86.07	$86.05	$86.10
Purchase #6	$240.60	8.184%	$260.2907	$260.29	$260.30	$260.30
Purchase #7	$90.97	9.526%	$99.6358	$99.64	$99.65	$99.60
7 purchase totals =	$960.46		$1,050.0368	$1,050.04	$1,050.05	$1,050.10