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	$81.82	10.257%	$90.2123	$90.21	$90.20	$90.20
Purchase #2	$185.48	4.836%	$194.4498	$194.45	$194.45	$194.40
Purchase #3	$213.86	8.441%	$231.9119	$231.91	$231.90	$231.90
Purchase #4	$78.64	10.129%	$86.6054	$86.61	$86.60	$86.60
Purchase #5	$150.75	12.355%	$169.3752	$169.38	$169.40	$169.40
Purchase #6	$197.68	9.817%	$217.0862	$217.09	$217.10	$217.10
Purchase #7	$109.84	8.285%	$118.9402	$118.94	$118.95	$118.90
7 purchase totals =	$1,018.07		$1,108.5810	$1,108.59	$1,108.60	$1,108.50