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	$78.75	4.766%	$82.5032	$82.50	$82.50	$82.50
Purchase #2	$190.56	7.609%	$205.0597	$205.06	$205.05	$205.10
Purchase #3	$80.33	6.567%	$85.6053	$85.61	$85.60	$85.60
Purchase #4	$224.33	7.702%	$241.6079	$241.61	$241.60	$241.60
Purchase #5	$91.88	7.807%	$99.0531	$99.05	$99.05	$99.10
Purchase #6	$157.83	5.370%	$166.3055	$166.31	$166.30	$166.30
Purchase #7	$49.90	9.681%	$54.7308	$54.73	$54.75	$54.70
7 purchase totals =	$873.58		$934.8655	$934.87	$934.85	$934.90