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	$6.56	5.332%	$6.9098	$6.91	$6.90	$6.90
Purchase #2	$71.59	9.384%	$78.308	$78.31	$78.30	$78.30
Purchase #3	$42.33	9.866%	$46.5063	$46.51	$46.50	$46.50
Purchase #4	$102.55	5.843%	$108.542	$108.54	$108.55	$108.50
Purchase #5	$57.53	12.484%	$64.712	$64.71	$64.70	$64.70
Purchase #6	$24.93	10.203%	$27.4736	$27.47	$27.45	$27.50
Purchase #7	$185.64	4.697%	$194.3595	$194.36	$194.35	$194.40
7 purchase totals =	$491.13		$526.8112	$526.81	$526.75	$526.80