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	$103.79	13.722%	$118.0321	$118.03	$118.05	$118.00
Purchase #2	$123.92	13.658%	$140.845	$140.85	$140.85	$140.80
Purchase #3	$69.34	6.566%	$73.8929	$73.89	$73.90	$73.90
Purchase #4	$101.78	10.329%	$112.2929	$112.29	$112.30	$112.30
Purchase #5	$137.28	11.327%	$152.8297	$152.83	$152.85	$152.80
Purchase #6	$191.79	10.427%	$211.7879	$211.79	$211.80	$211.80
Purchase #7	$197.94	9.516%	$216.776	$216.78	$216.80	$216.80
7 purchase totals =	$925.84		$1,026.4565	$1,026.46	$1,026.55	$1,026.40