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	$65.46	3.412%	$67.6935	$67.69	$67.70	$67.70
Purchase #2	$81.63	5.231%	$85.9001	$85.90	$85.90	$85.90
Purchase #3	$154.67	13.204%	$175.0926	$175.09	$175.10	$175.10
Purchase #4	$218.33	11.206%	$242.7961	$242.80	$242.80	$242.80
Purchase #5	$57.28	3.615%	$59.3507	$59.35	$59.35	$59.40
Purchase #6	$102.55	8.711%	$111.4831	$111.48	$111.50	$111.50
Purchase #7	$237.63	11.738%	$265.523	$265.52	$265.50	$265.50
7 purchase totals =	$917.55		$1,007.8391	$1,007.83	$1,007.85	$1,007.90