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	$142.72	5.223%	$150.1743	$150.17	$150.15	$150.20
Purchase #2	$12.64	10.119%	$13.919	$13.92	$13.90	$13.90
Purchase #3	$160.52	3.826%	$166.6615	$166.66	$166.65	$166.70
Purchase #4	$32.31	6.440%	$34.3908	$34.39	$34.40	$34.40
Purchase #5	$190.34	8.379%	$206.2886	$206.29	$206.30	$206.30
Purchase #6	$240.37	7.834%	$259.2006	$259.20	$259.20	$259.20
Purchase #7	$55.57	7.803%	$59.9061	$59.91	$59.90	$59.90
7 purchase totals =	$834.47		$890.5409	$890.54	$890.50	$890.60