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	$91.48	7.741%	$98.5615	$98.56	$98.55	$98.60
Purchase #2	$29.54	5.874%	$31.2752	$31.28	$31.30	$31.30
Purchase #3	$56.49	12.579%	$63.5959	$63.60	$63.60	$63.60
Purchase #4	$78.61	9.162%	$85.8122	$85.81	$85.80	$85.80
Purchase #5	$93.37	11.102%	$103.7359	$103.74	$103.75	$103.70
Purchase #6	$60.73	6.143%	$64.4606	$64.46	$64.45	$64.50
Purchase #7	$216.98	11.823%	$242.6335	$242.63	$242.65	$242.60
7 purchase totals =	$627.20		$690.0748	$690.08	$690.10	$690.10