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	$88.38	11.570%	$98.6056	$98.61	$98.60	$98.60
Purchase #2	$42.64	10.165%	$46.9744	$46.97	$46.95	$47.00
Purchase #3	$115.84	10.772%	$128.3183	$128.32	$128.30	$128.30
Purchase #4	$162.49	6.859%	$173.6352	$173.64	$173.65	$173.60
Purchase #5	$66.71	4.814%	$69.9214	$69.92	$69.90	$69.90
Purchase #6	$244.76	5.427%	$258.0431	$258.04	$258.05	$258.00
Purchase #7	$196.92	12.768%	$222.0627	$222.06	$222.05	$222.10
7 purchase totals =	$917.74		$997.5607	$997.56	$997.50	$997.50