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	$89.40	13.536%	$101.5012	$101.50	$101.50	$101.50
Purchase #2	$152.29	6.290%	$161.869	$161.87	$161.85	$161.90
Purchase #3	$86.43	4.873%	$90.6417	$90.64	$90.65	$90.60
Purchase #4	$156.54	11.541%	$174.6063	$174.61	$174.60	$174.60
Purchase #5	$236.50	8.772%	$257.2458	$257.25	$257.25	$257.20
Purchase #6	$59.48	12.737%	$67.056	$67.06	$67.05	$67.10
Purchase #7	$233.39	5.249%	$245.6406	$245.64	$245.65	$245.60
7 purchase totals =	$1,014.03		$1,098.5606	$1,098.57	$1,098.55	$1,098.50