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	$98.72	6.738%	$105.3718	$105.37	$105.35	$105.40
Purchase #2	$163.84	13.196%	$185.4603	$185.46	$185.45	$185.50
Purchase #3	$249.42	11.731%	$278.6795	$278.68	$278.70	$278.70
Purchase #4	$193.43	10.448%	$213.6396	$213.64	$213.65	$213.60
Purchase #5	$191.60	12.627%	$215.7933	$215.79	$215.80	$215.80
Purchase #6	$29.89	10.288%	$32.9651	$32.97	$32.95	$33.00
Purchase #7	$74.79	10.708%	$82.7985	$82.80	$82.80	$82.80
7 purchase totals =	$1,001.69		$1,114.7081	$1,114.71	$1,114.70	$1,114.80