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	$211.93	5.643%	$223.8892	$223.89	$223.90	$223.90
Purchase #2	$198.59	5.114%	$208.7459	$208.75	$208.75	$208.70
Purchase #3	$122.70	3.132%	$126.543	$126.54	$126.55	$126.50
Purchase #4	$234.60	13.500%	$266.271	$266.27	$266.25	$266.30
Purchase #5	$134.31	11.743%	$150.082	$150.08	$150.10	$150.10
Purchase #6	$163.48	4.840%	$171.3924	$171.39	$171.40	$171.40
Purchase #7	$159.28	10.434%	$175.8993	$175.90	$175.90	$175.90
7 purchase totals =	$1,224.89		$1,322.8228	$1,322.82	$1,322.85	$1,322.80