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	$187.65	3.678%	$194.5518	$194.55	$194.55	$194.60
Purchase #2	$106.97	12.299%	$120.1262	$120.13	$120.15	$120.10
Purchase #3	$72.64	7.866%	$78.3539	$78.35	$78.35	$78.40
Purchase #4	$30.93	10.156%	$34.0713	$34.07	$34.05	$34.10
Purchase #5	$128.71	8.371%	$139.4843	$139.48	$139.50	$139.50
Purchase #6	$193.82	3.637%	$200.8692	$200.87	$200.85	$200.90
Purchase #7	$225.40	11.813%	$252.0265	$252.03	$252.05	$252.00
7 purchase totals =	$946.12		$1,019.4832	$1,019.48	$1,019.50	$1,019.60