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	$165.77	10.231%	$182.7299	$182.73	$182.75	$182.70
Purchase #2	$17.38	5.789%	$18.3861	$18.39	$18.40	$18.40
Purchase #3	$165.59	11.458%	$184.5633	$184.56	$184.55	$184.60
Purchase #4	$188.30	7.519%	$202.4583	$202.46	$202.45	$202.50
Purchase #5	$178.25	11.243%	$198.2906	$198.29	$198.30	$198.30
Purchase #6	$31.47	13.134%	$35.6033	$35.60	$35.60	$35.60
Purchase #7	$90.96	4.258%	$94.8331	$94.83	$94.85	$94.80
7 purchase totals =	$837.72		$916.8646	$916.86	$916.90	$916.90