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	$43.59	6.134%	$46.2638	$46.26	$46.25	$46.30
Purchase #2	$28.25	9.234%	$30.8586	$30.86	$30.85	$30.90
Purchase #3	$121.95	7.564%	$131.1743	$131.17	$131.15	$131.20
Purchase #4	$90.80	8.242%	$98.2837	$98.28	$98.30	$98.30
Purchase #5	$109.90	7.628%	$118.2832	$118.28	$118.30	$118.30
Purchase #6	$160.90	9.289%	$175.846	$175.85	$175.85	$175.80
Purchase #7	$189.30	5.696%	$200.0825	$200.08	$200.10	$200.10
7 purchase totals =	$744.69		$800.7921	$800.78	$800.80	$800.90