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	$63.58	9.301%	$69.4936	$69.49	$69.50	$69.50
Purchase #2	$221.47	10.708%	$245.185	$245.19	$245.20	$245.20
Purchase #3	$190.44	5.303%	$200.539	$200.54	$200.55	$200.50
Purchase #4	$119.50	9.284%	$130.5944	$130.59	$130.60	$130.60
Purchase #5	$96.32	3.662%	$99.8472	$99.85	$99.85	$99.80
Purchase #6	$42.40	5.797%	$44.8579	$44.86	$44.85	$44.90
Purchase #7	$67.85	7.144%	$72.6972	$72.70	$72.70	$72.70
7 purchase totals =	$801.56		$863.2143	$863.22	$863.25	$863.20