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	$34.83	4.841%	$36.5161	$36.52	$36.50	$36.50
Purchase #2	$170.38	10.842%	$188.8526	$188.85	$188.85	$188.90
Purchase #3	$223.70	3.672%	$231.9143	$231.91	$231.90	$231.90
Purchase #4	$211.78	11.411%	$235.9462	$235.95	$235.95	$235.90
Purchase #5	$151.44	6.222%	$160.8626	$160.86	$160.85	$160.90
Purchase #6	$57.69	3.296%	$59.5915	$59.59	$59.60	$59.60
Purchase #7	$186.80	9.751%	$205.0149	$205.01	$205.00	$205.00
7 purchase totals =	$1,036.62		$1,118.6982	$1,118.69	$1,118.65	$1,118.70