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	$184.77	13.479%	$209.6751	$209.68	$209.70	$209.70
Purchase #2	$163.75	11.501%	$182.5829	$182.58	$182.60	$182.60
Purchase #3	$18.63	6.756%	$19.8886	$19.89	$19.90	$19.90
Purchase #4	$76.56	8.246%	$82.8731	$82.87	$82.85	$82.90
Purchase #5	$115.67	6.758%	$123.487	$123.49	$123.50	$123.50
Purchase #6	$215.97	5.181%	$227.1594	$227.16	$227.15	$227.20
Purchase #7	$170.86	10.627%	$189.0173	$189.02	$189.00	$189.00
7 purchase totals =	$946.21		$1,034.6834	$1,034.69	$1,034.70	$1,034.80