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	$73.43	9.698%	$80.5512	$80.55	$80.55	$80.60
Purchase #2	$123.56	7.138%	$132.3797	$132.38	$132.40	$132.40
Purchase #3	$225.28	8.638%	$244.7397	$244.74	$244.75	$244.70
Purchase #4	$32.94	8.391%	$35.704	$35.70	$35.70	$35.70
Purchase #5	$126.75	10.160%	$139.6278	$139.63	$139.65	$139.60
Purchase #6	$188.78	4.142%	$196.5993	$196.60	$196.60	$196.60
Purchase #7	$152.98	12.269%	$171.7491	$171.75	$171.75	$171.70
7 purchase totals =	$923.72		$1,001.3508	$1,001.35	$1,001.40	$1,001.30