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	$35.56	9.557%	$38.9585	$38.96	$38.95	$39.00
Purchase #2	$120.42	6.252%	$127.9487	$127.95	$127.95	$127.90
Purchase #3	$184.68	4.146%	$192.3368	$192.34	$192.35	$192.30
Purchase #4	$55.52	7.356%	$59.6041	$59.60	$59.60	$59.60
Purchase #5	$72.68	6.326%	$77.2777	$77.28	$77.30	$77.30
Purchase #6	$27.29	13.742%	$31.0402	$31.04	$31.05	$31.00
Purchase #7	$239.41	12.492%	$269.3171	$269.32	$269.30	$269.30
7 purchase totals =	$735.56		$796.4831	$796.49	$796.50	$796.40