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	$13.85	12.766%	$15.6181	$15.62	$15.60	$15.60
Purchase #2	$154.37	6.745%	$164.7823	$164.78	$164.80	$164.80
Purchase #3	$70.39	13.505%	$79.8962	$79.90	$79.90	$79.90
Purchase #4	$248.94	3.501%	$257.6554	$257.66	$257.65	$257.70
Purchase #5	$156.37	11.620%	$174.5402	$174.54	$174.55	$174.50
Purchase #6	$172.34	11.112%	$191.4904	$191.49	$191.50	$191.50
Purchase #7	$153.51	12.138%	$172.143	$172.14	$172.15	$172.10
7 purchase totals =	$969.77		$1,056.1256	$1,056.13	$1,056.15	$1,056.10