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	$241.39	7.637%	$259.825	$259.83	$259.85	$259.80
Purchase #2	$117.36	8.585%	$127.4354	$127.44	$127.45	$127.40
Purchase #3	$184.80	3.353%	$190.9963	$191.00	$191.00	$191.00
Purchase #4	$54.39	3.718%	$56.4122	$56.41	$56.40	$56.40
Purchase #5	$47.87	13.803%	$54.4775	$54.48	$54.50	$54.50
Purchase #6	$77.47	8.735%	$84.237	$84.24	$84.25	$84.20
Purchase #7	$57.76	3.758%	$59.9306	$59.93	$59.95	$59.90
7 purchase totals =	$781.04		$833.3140	$833.33	$833.40	$833.20