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	$162.54	4.824%	$170.3809	$170.38	$170.40	$170.40
Purchase #2	$229.62	9.668%	$251.8197	$251.82	$251.80	$251.80
Purchase #3	$68.85	4.530%	$71.9689	$71.97	$71.95	$72.00
Purchase #4	$131.95	5.419%	$139.1004	$139.10	$139.10	$139.10
Purchase #5	$154.89	6.135%	$164.3925	$164.39	$164.40	$164.40
Purchase #6	$137.86	3.647%	$142.8878	$142.89	$142.90	$142.90
Purchase #7	$13.39	3.154%	$13.8123	$13.81	$13.80	$13.80
7 purchase totals =	$899.10		$954.3625	$954.36	$954.35	$954.40