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	$153.51	3.336%	$158.6311	$158.63	$158.65	$158.60
Purchase #2	$250.50	9.108%	$273.3155	$273.32	$273.30	$273.30
Purchase #3	$78.73	5.337%	$82.9318	$82.93	$82.95	$82.90
Purchase #4	$78.60	12.419%	$88.3613	$88.36	$88.35	$88.40
Purchase #5	$246.88	11.601%	$275.5205	$275.52	$275.50	$275.50
Purchase #6	$45.68	6.271%	$48.5446	$48.54	$48.55	$48.50
Purchase #7	$145.58	12.215%	$163.3626	$163.36	$163.35	$163.40
7 purchase totals =	$999.48		$1,090.6674	$1,090.66	$1,090.65	$1,090.60