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	$52.83	6.567%	$56.2993	$56.30	$56.30	$56.30
Purchase #2	$28.42	11.787%	$31.7699	$31.77	$31.75	$31.80
Purchase #3	$11.48	12.443%	$12.9085	$12.91	$12.90	$12.90
Purchase #4	$24.33	12.272%	$27.3158	$27.32	$27.30	$27.30
Purchase #5	$94.29	9.539%	$103.2843	$103.28	$103.30	$103.30
Purchase #6	$99.73	13.201%	$112.8954	$112.90	$112.90	$112.90
Purchase #7	$65.68	6.563%	$69.9906	$69.99	$70.00	$70.00
7 purchase totals =	$376.76		$414.4638	$414.47	$414.45	$414.50