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	$209.89	11.172%	$233.3389	$233.34	$233.35	$233.30
Purchase #2	$103.41	11.847%	$115.661	$115.66	$115.65	$115.70
Purchase #3	$133.52	11.412%	$148.7573	$148.76	$148.75	$148.80
Purchase #4	$49.81	4.108%	$51.8562	$51.86	$51.85	$51.90
Purchase #5	$98.59	9.776%	$108.2282	$108.23	$108.25	$108.20
Purchase #6	$62.29	8.844%	$67.7989	$67.80	$67.80	$67.80
Purchase #7	$165.26	6.417%	$175.8647	$175.86	$175.85	$175.90
7 purchase totals =	$822.77		$901.5052	$901.51	$901.50	$901.60