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	$219.56	8.179%	$237.5178	$237.52	$237.50	$237.50
Purchase #2	$232.93	3.311%	$240.6423	$240.64	$240.65	$240.60
Purchase #3	$150.76	13.791%	$171.5513	$171.55	$171.55	$171.60
Purchase #4	$104.25	9.329%	$113.9755	$113.98	$114.00	$114.00
Purchase #5	$71.56	6.667%	$76.3309	$76.33	$76.35	$76.30
Purchase #6	$44.84	6.845%	$47.9093	$47.91	$47.90	$47.90
Purchase #7	$104.79	11.312%	$116.6438	$116.64	$116.65	$116.60
7 purchase totals =	$928.69		$1,004.5709	$1,004.57	$1,004.60	$1,004.50