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	$236.96	12.430%	$266.4141	$266.41	$266.40	$266.40
Purchase #2	$52.45	13.223%	$59.3855	$59.39	$59.40	$59.40
Purchase #3	$199.25	8.141%	$215.4709	$215.47	$215.45	$215.50
Purchase #4	$216.60	4.696%	$226.7715	$226.77	$226.75	$226.80
Purchase #5	$35.28	9.653%	$38.6856	$38.69	$38.70	$38.70
Purchase #6	$213.82	6.520%	$227.7611	$227.76	$227.75	$227.80
Purchase #7	$57.37	6.503%	$61.1008	$61.10	$61.10	$61.10
7 purchase totals =	$1,011.73		$1,095.5895	$1,095.59	$1,095.55	$1,095.70