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	$238.57	8.815%	$259.5999	$259.60	$259.60	$259.60
Purchase #2	$83.35	7.497%	$89.5987	$89.60	$89.60	$89.60
Purchase #3	$113.52	12.521%	$127.7338	$127.73	$127.75	$127.70
Purchase #4	$55.50	6.720%	$59.2296	$59.23	$59.25	$59.20
Purchase #5	$59.53	13.855%	$67.7779	$67.78	$67.80	$67.80
Purchase #6	$243.63	12.460%	$273.9863	$273.99	$274.00	$274.00
Purchase #7	$248.62	7.375%	$266.9557	$266.96	$266.95	$267.00
7 purchase totals =	$1,042.72		$1,144.8819	$1,144.89	$1,144.95	$1,144.90