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	$241.38	5.158%	$253.8304	$253.83	$253.85	$253.80
Purchase #2	$181.58	13.282%	$205.6975	$205.70	$205.70	$205.70
Purchase #3	$57.61	13.526%	$65.4023	$65.40	$65.40	$65.40
Purchase #4	$150.55	12.140%	$168.8268	$168.83	$168.85	$168.80
Purchase #5	$137.42	8.320%	$148.8533	$148.85	$148.85	$148.90
Purchase #6	$110.99	4.448%	$115.9268	$115.93	$115.95	$115.90
Purchase #7	$188.59	4.248%	$196.6013	$196.60	$196.60	$196.60
7 purchase totals =	$1,068.12		$1,155.1384	$1,155.14	$1,155.20	$1,155.10