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	$215.94	7.388%	$231.8936	$231.89	$231.90	$231.90
Purchase #2	$232.79	6.539%	$248.0121	$248.01	$248.00	$248.00
Purchase #3	$33.49	4.145%	$34.8782	$34.88	$34.90	$34.90
Purchase #4	$102.52	8.227%	$110.9543	$110.95	$110.95	$111.00
Purchase #5	$49.72	9.391%	$54.3892	$54.39	$54.40	$54.40
Purchase #6	$219.34	11.486%	$244.5334	$244.53	$244.55	$244.50
Purchase #7	$155.92	4.449%	$162.8569	$162.86	$162.85	$162.90
7 purchase totals =	$1,009.72		$1,087.5177	$1,087.51	$1,087.55	$1,087.60