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	$87.48	12.748%	$98.632	$98.63	$98.65	$98.60
Purchase #2	$63.25	6.800%	$67.551	$67.55	$67.55	$67.60
Purchase #3	$140.55	7.623%	$151.2641	$151.26	$151.25	$151.30
Purchase #4	$176.97	13.321%	$200.5442	$200.54	$200.55	$200.50
Purchase #5	$223.58	5.677%	$236.2726	$236.27	$236.25	$236.30
Purchase #6	$80.46	10.779%	$89.1328	$89.13	$89.15	$89.10
Purchase #7	$85.49	6.253%	$90.8357	$90.84	$90.85	$90.80
7 purchase totals =	$857.78		$934.2324	$934.22	$934.25	$934.20