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	$64.47	12.847%	$72.7525	$72.75	$72.75	$72.80
Purchase #2	$158.61	3.554%	$164.247	$164.25	$164.25	$164.20
Purchase #3	$113.95	6.232%	$121.0514	$121.05	$121.05	$121.10
Purchase #4	$204.69	8.835%	$222.7744	$222.77	$222.75	$222.80
Purchase #5	$198.80	3.559%	$205.8753	$205.88	$205.90	$205.90
Purchase #6	$161.25	4.280%	$168.1515	$168.15	$168.15	$168.20
Purchase #7	$203.96	13.313%	$231.1132	$231.11	$231.10	$231.10
7 purchase totals =	$1,105.73		$1,185.9653	$1,185.96	$1,185.95	$1,186.10