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	$57.80	3.373%	$59.7496	$59.75	$59.75	$59.70
Purchase #2	$114.89	4.801%	$120.4059	$120.41	$120.40	$120.40
Purchase #3	$31.67	12.749%	$35.7076	$35.71	$35.70	$35.70
Purchase #4	$40.98	10.832%	$45.419	$45.42	$45.40	$45.40
Purchase #5	$85.34	9.477%	$93.4277	$93.43	$93.45	$93.40
Purchase #6	$182.39	6.845%	$194.8746	$194.87	$194.85	$194.90
Purchase #7	$94.50	7.206%	$101.3097	$101.31	$101.30	$101.30
7 purchase totals =	$607.57		$650.8941	$650.90	$650.85	$650.80