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	$104.53	7.674%	$112.5516	$112.55	$112.55	$112.60
Purchase #2	$54.47	3.822%	$56.5518	$56.55	$56.55	$56.60
Purchase #3	$152.50	9.822%	$167.4786	$167.48	$167.50	$167.50
Purchase #4	$47.73	10.318%	$52.6548	$52.65	$52.65	$52.70
Purchase #5	$87.74	10.745%	$97.1677	$97.17	$97.15	$97.20
Purchase #6	$145.93	5.739%	$154.3049	$154.30	$154.30	$154.30
Purchase #7	$112.90	12.815%	$127.3681	$127.37	$127.35	$127.40
7 purchase totals =	$705.80		$768.0775	$768.07	$768.05	$768.30