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	$213.58	5.278%	$224.8528	$224.85	$224.85	$224.90
Purchase #2	$172.78	12.435%	$194.2652	$194.27	$194.25	$194.30
Purchase #3	$140.26	7.527%	$150.8174	$150.82	$150.80	$150.80
Purchase #4	$197.44	6.504%	$210.2815	$210.28	$210.30	$210.30
Purchase #5	$79.75	13.353%	$90.399	$90.40	$90.40	$90.40
Purchase #6	$157.55	4.401%	$164.4838	$164.48	$164.50	$164.50
Purchase #7	$75.80	13.814%	$86.271	$86.27	$86.25	$86.30
7 purchase totals =	$1,037.16		$1,121.3707	$1,121.37	$1,121.35	$1,121.50