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	$123.94	3.816%	$128.6696	$128.67	$128.65	$128.70
Purchase #2	$157.96	13.335%	$179.024	$179.02	$179.00	$179.00
Purchase #3	$140.81	7.537%	$151.4228	$151.42	$151.40	$151.40
Purchase #4	$56.71	4.525%	$59.2761	$59.28	$59.30	$59.30
Purchase #5	$184.84	12.250%	$207.4829	$207.48	$207.50	$207.50
Purchase #6	$144.94	7.271%	$155.4786	$155.48	$155.50	$155.50
Purchase #7	$167.65	7.481%	$180.1919	$180.19	$180.20	$180.20
7 purchase totals =	$976.85		$1,061.5459	$1,061.54	$1,061.55	$1,061.60