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	$127.83	10.767%	$141.5935	$141.59	$141.60	$141.60
Purchase #2	$17.37	8.307%	$18.8129	$18.81	$18.80	$18.80
Purchase #3	$45.96	3.577%	$47.604	$47.60	$47.60	$47.60
Purchase #4	$196.96	6.780%	$210.3139	$210.31	$210.30	$210.30
Purchase #5	$119.73	7.872%	$129.1551	$129.16	$129.15	$129.20
Purchase #6	$105.37	6.643%	$112.3697	$112.37	$112.35	$112.40
Purchase #7	$128.58	6.227%	$136.5867	$136.59	$136.60	$136.60
7 purchase totals =	$741.80		$796.4358	$796.43	$796.40	$796.50