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	$241.31	11.576%	$269.244	$269.24	$269.25	$269.20
Purchase #2	$200.83	9.595%	$220.0996	$220.10	$220.10	$220.10
Purchase #3	$87.84	13.582%	$99.7704	$99.77	$99.75	$99.80
Purchase #4	$199.65	9.851%	$219.3175	$219.32	$219.30	$219.30
Purchase #5	$147.34	6.102%	$156.3307	$156.33	$156.35	$156.30
Purchase #6	$10.94	4.774%	$11.4623	$11.46	$11.45	$11.50
Purchase #7	$190.50	3.175%	$196.5484	$196.55	$196.55	$196.50
7 purchase totals =	$1,078.41		$1,172.7729	$1,172.77	$1,172.75	$1,172.70