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	$86.90	3.139%	$89.6278	$89.63	$89.65	$89.60
Purchase #2	$197.93	7.544%	$212.8618	$212.86	$212.85	$212.90
Purchase #3	$157.39	5.206%	$165.5837	$165.58	$165.60	$165.60
Purchase #4	$172.46	10.746%	$190.9926	$190.99	$191.00	$191.00
Purchase #5	$128.60	4.111%	$133.8867	$133.89	$133.90	$133.90
Purchase #6	$50.46	5.384%	$53.1768	$53.18	$53.20	$53.20
Purchase #7	$198.53	7.226%	$212.8758	$212.88	$212.90	$212.90
7 purchase totals =	$992.27		$1,059.0052	$1,059.01	$1,059.10	$1,059.10