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	$179.69	12.699%	$202.5088	$202.51	$202.50	$202.50
Purchase #2	$143.65	7.142%	$153.9095	$153.91	$153.90	$153.90
Purchase #3	$143.93	12.772%	$162.3127	$162.31	$162.30	$162.30
Purchase #4	$142.39	6.705%	$151.9372	$151.94	$151.95	$151.90
Purchase #5	$61.89	13.334%	$70.1424	$70.14	$70.15	$70.10
Purchase #6	$99.46	5.371%	$104.802	$104.80	$104.80	$104.80
Purchase #7	$25.83	12.591%	$29.0823	$29.08	$29.10	$29.10
7 purchase totals =	$796.84		$874.6949	$874.69	$874.70	$874.60