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	$207.55	7.566%	$223.2532	$223.25	$223.25	$223.30
Purchase #2	$50.85	12.384%	$57.1473	$57.15	$57.15	$57.10
Purchase #3	$164.64	12.594%	$185.3748	$185.37	$185.35	$185.40
Purchase #4	$91.65	7.526%	$98.5476	$98.55	$98.55	$98.50
Purchase #5	$28.71	10.769%	$31.8018	$31.80	$31.80	$31.80
Purchase #6	$169.87	8.355%	$184.0626	$184.06	$184.05	$184.10
Purchase #7	$228.54	12.436%	$256.9612	$256.96	$256.95	$257.00
7 purchase totals =	$941.81		$1,037.1485	$1,037.14	$1,037.10	$1,037.20