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	$119.67	6.538%	$127.494	$127.49	$127.50	$127.50
Purchase #2	$78.85	7.622%	$84.8599	$84.86	$84.85	$84.90
Purchase #3	$205.54	10.860%	$227.8616	$227.86	$227.85	$227.90
Purchase #4	$25.74	7.232%	$27.6015	$27.60	$27.60	$27.60
Purchase #5	$42.88	6.629%	$45.7225	$45.72	$45.70	$45.70
Purchase #6	$148.92	11.457%	$165.9818	$165.98	$166.00	$166.00
Purchase #7	$137.74	3.200%	$142.1477	$142.15	$142.15	$142.10
7 purchase totals =	$759.34		$821.6690	$821.66	$821.65	$821.70