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	$229.66	11.412%	$255.8688	$255.87	$255.85	$255.90
Purchase #2	$167.80	10.397%	$185.2462	$185.25	$185.25	$185.20
Purchase #3	$199.58	7.718%	$214.9836	$214.98	$215.00	$215.00
Purchase #4	$162.41	3.618%	$168.286	$168.29	$168.30	$168.30
Purchase #5	$124.68	5.768%	$131.8715	$131.87	$131.85	$131.90
Purchase #6	$82.63	11.579%	$92.1977	$92.20	$92.20	$92.20
Purchase #7	$42.27	13.323%	$47.9016	$47.90	$47.90	$47.90
7 purchase totals =	$1,009.03		$1,096.3554	$1,096.36	$1,096.35	$1,096.40