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	$216.27	5.840%	$228.9002	$228.90	$228.90	$228.90
Purchase #2	$180.55	13.465%	$204.8611	$204.86	$204.85	$204.90
Purchase #3	$85.60	5.597%	$90.391	$90.39	$90.40	$90.40
Purchase #4	$10.86	3.680%	$11.2596	$11.26	$11.25	$11.30
Purchase #5	$47.81	8.837%	$52.035	$52.04	$52.05	$52.00
Purchase #6	$62.52	7.359%	$67.1208	$67.12	$67.10	$67.10
Purchase #7	$192.72	5.816%	$203.9286	$203.93	$203.95	$203.90
7 purchase totals =	$796.33		$858.4963	$858.50	$858.50	$858.50