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	$58.53	10.826%	$64.8665	$64.87	$64.85	$64.90
Purchase #2	$91.89	11.104%	$102.0935	$102.09	$102.10	$102.10
Purchase #3	$196.54	6.392%	$209.1028	$209.10	$209.10	$209.10
Purchase #4	$173.31	3.601%	$179.5509	$179.55	$179.55	$179.60
Purchase #5	$63.91	4.702%	$66.915	$66.92	$66.90	$66.90
Purchase #6	$200.28	8.745%	$217.7945	$217.79	$217.80	$217.80
Purchase #7	$232.28	3.417%	$240.217	$240.22	$240.20	$240.20
7 purchase totals =	$1,016.74		$1,080.5402	$1,080.54	$1,080.50	$1,080.60