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	$172.96	10.164%	$190.5397	$190.54	$190.55	$190.50
Purchase #2	$246.31	7.159%	$263.9433	$263.94	$263.95	$263.90
Purchase #3	$12.29	4.394%	$12.83	$12.83	$12.85	$12.80
Purchase #4	$59.86	12.382%	$67.2719	$67.27	$67.25	$67.30
Purchase #5	$241.96	10.662%	$267.7578	$267.76	$267.75	$267.80
Purchase #6	$47.81	4.808%	$50.1087	$50.11	$50.10	$50.10
Purchase #7	$99.50	11.176%	$110.6201	$110.62	$110.60	$110.60
7 purchase totals =	$880.69		$963.0715	$963.07	$963.05	$963.00