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	$68.76	4.268%	$71.6947	$71.69	$71.70	$71.70
Purchase #2	$196.48	11.641%	$219.3522	$219.35	$219.35	$219.40
Purchase #3	$166.85	10.797%	$184.8648	$184.86	$184.85	$184.90
Purchase #4	$187.96	13.866%	$214.0225	$214.02	$214.00	$214.00
Purchase #5	$109.45	6.213%	$116.2501	$116.25	$116.25	$116.30
Purchase #6	$154.50	8.794%	$168.0867	$168.09	$168.10	$168.10
Purchase #7	$81.65	9.247%	$89.2002	$89.20	$89.20	$89.20
7 purchase totals =	$965.65		$1,063.4712	$1,063.46	$1,063.45	$1,063.60