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	$196.67	6.314%	$209.0877	$209.09	$209.10	$209.10
Purchase #2	$174.80	4.324%	$182.3584	$182.36	$182.35	$182.40
Purchase #3	$127.35	5.761%	$134.6866	$134.69	$134.70	$134.70
Purchase #4	$176.86	11.360%	$196.9513	$196.95	$196.95	$197.00
Purchase #5	$34.48	9.504%	$37.757	$37.76	$37.75	$37.80
Purchase #6	$43.64	6.199%	$46.3452	$46.35	$46.35	$46.30
Purchase #7	$246.38	11.454%	$274.6004	$274.60	$274.60	$274.60
7 purchase totals =	$1,000.18		$1,081.7866	$1,081.80	$1,081.80	$1,081.90