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	$182.86	6.580%	$194.8922	$194.89	$194.90	$194.90
Purchase #2	$110.83	3.607%	$114.8276	$114.83	$114.85	$114.80
Purchase #3	$222.82	13.703%	$253.353	$253.35	$253.35	$253.40
Purchase #4	$212.47	10.635%	$235.0662	$235.07	$235.05	$235.10
Purchase #5	$246.30	10.271%	$271.5975	$271.60	$271.60	$271.60
Purchase #6	$181.78	9.139%	$198.3929	$198.39	$198.40	$198.40
Purchase #7	$229.34	11.478%	$255.6636	$255.66	$255.65	$255.70
7 purchase totals =	$1,386.40		$1,523.7930	$1,523.79	$1,523.80	$1,523.90