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	$184.43	13.352%	$209.0551	$209.06	$209.05	$209.10
Purchase #2	$124.96	10.819%	$138.4794	$138.48	$138.50	$138.50
Purchase #3	$142.83	6.151%	$151.6155	$151.62	$151.60	$151.60
Purchase #4	$94.82	11.120%	$105.364	$105.36	$105.35	$105.40
Purchase #5	$63.76	10.188%	$70.2559	$70.26	$70.25	$70.30
Purchase #6	$208.49	5.720%	$220.4156	$220.42	$220.40	$220.40
Purchase #7	$223.80	11.196%	$248.8566	$248.86	$248.85	$248.90
7 purchase totals =	$1,043.09		$1,144.0421	$1,144.06	$1,144.00	$1,144.20