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	$78.51	10.633%	$86.858	$86.86	$86.85	$86.90
Purchase #2	$9.43	13.369%	$10.6907	$10.69	$10.70	$10.70
Purchase #3	$139.70	3.456%	$144.528	$144.53	$144.55	$144.50
Purchase #4	$223.72	5.269%	$235.5078	$235.51	$235.50	$235.50
Purchase #5	$41.88	6.483%	$44.5951	$44.60	$44.60	$44.60
Purchase #6	$191.54	9.854%	$210.4144	$210.41	$210.40	$210.40
Purchase #7	$111.56	6.774%	$119.1171	$119.12	$119.10	$119.10
7 purchase totals =	$796.34		$851.7111	$851.72	$851.70	$851.70