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	$89.86	10.844%	$99.6044	$99.60	$99.60	$99.60
Purchase #2	$58.97	8.410%	$63.9294	$63.93	$63.95	$63.90
Purchase #3	$12.88	13.158%	$14.5748	$14.57	$14.55	$14.60
Purchase #4	$208.53	4.320%	$217.5385	$217.54	$217.55	$217.50
Purchase #5	$244.73	10.227%	$269.7585	$269.76	$269.75	$269.80
Purchase #6	$190.33	9.485%	$208.3828	$208.38	$208.40	$208.40
Purchase #7	$71.47	7.811%	$77.0525	$77.05	$77.05	$77.10
7 purchase totals =	$876.77		$950.8409	$950.83	$950.85	$950.90