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	$116.63	13.434%	$132.2981	$132.30	$132.30	$132.30
Purchase #2	$134.88	4.408%	$140.8255	$140.83	$140.85	$140.80
Purchase #3	$64.57	13.263%	$73.1339	$73.13	$73.15	$73.10
Purchase #4	$37.69	8.534%	$40.9065	$40.91	$40.90	$40.90
Purchase #5	$176.59	13.577%	$200.5656	$200.57	$200.55	$200.60
Purchase #6	$70.41	3.557%	$72.9145	$72.91	$72.90	$72.90
Purchase #7	$86.72	5.765%	$91.7194	$91.72	$91.70	$91.70
7 purchase totals =	$687.49		$752.3635	$752.37	$752.35	$752.30