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	$169.51	10.148%	$186.7119	$186.71	$186.70	$186.70
Purchase #2	$209.36	11.430%	$233.2898	$233.29	$233.30	$233.30
Purchase #3	$102.98	13.225%	$116.5991	$116.60	$116.60	$116.60
Purchase #4	$85.55	12.162%	$95.9546	$95.95	$95.95	$96.00
Purchase #5	$129.95	12.720%	$146.4796	$146.48	$146.50	$146.50
Purchase #6	$82.92	6.726%	$88.4972	$88.50	$88.50	$88.50
Purchase #7	$173.67	3.798%	$180.266	$180.27	$180.25	$180.30
7 purchase totals =	$953.94		$1,047.7982	$1,047.80	$1,047.80	$1,047.90