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	$215.51	10.445%	$238.02	$238.02	$238.00	$238.00
Purchase #2	$29.50	10.109%	$32.4822	$32.48	$32.50	$32.50
Purchase #3	$166.76	10.449%	$184.1848	$184.18	$184.20	$184.20
Purchase #4	$51.35	5.770%	$54.3129	$54.31	$54.30	$54.30
Purchase #5	$56.49	7.869%	$60.9352	$60.94	$60.95	$60.90
Purchase #6	$51.90	9.592%	$56.8782	$56.88	$56.90	$56.90
Purchase #7	$35.61	3.401%	$36.8211	$36.82	$36.80	$36.80
7 purchase totals =	$607.12		$663.6344	$663.63	$663.65	$663.60