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	$46.26	12.480%	$52.0332	$52.03	$52.05	$52.00
Purchase #2	$223.48	7.199%	$239.5683	$239.57	$239.55	$239.60
Purchase #3	$181.36	7.285%	$194.5721	$194.57	$194.55	$194.60
Purchase #4	$79.31	9.563%	$86.8944	$86.89	$86.90	$86.90
Purchase #5	$151.77	4.451%	$158.5253	$158.53	$158.55	$158.50
Purchase #6	$202.52	10.585%	$223.9567	$223.96	$223.95	$224.00
Purchase #7	$133.73	8.508%	$145.1077	$145.11	$145.10	$145.10
7 purchase totals =	$1,018.43		$1,100.6577	$1,100.66	$1,100.65	$1,100.70