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	$221.69	8.504%	$240.5425	$240.54	$240.55	$240.50
Purchase #2	$165.50	5.801%	$175.1007	$175.10	$175.10	$175.10
Purchase #3	$145.77	10.549%	$161.1473	$161.15	$161.15	$161.10
Purchase #4	$62.87	7.712%	$67.7185	$67.72	$67.70	$67.70
Purchase #5	$74.77	5.350%	$78.7702	$78.77	$78.75	$78.80
Purchase #6	$78.94	9.579%	$86.5017	$86.50	$86.50	$86.50
Purchase #7	$218.54	8.829%	$237.8349	$237.83	$237.85	$237.80
7 purchase totals =	$968.08		$1,047.6158	$1,047.61	$1,047.60	$1,047.50