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	$131.33	9.745%	$144.1281	$144.13	$144.15	$144.10
Purchase #2	$105.48	6.424%	$112.256	$112.26	$112.25	$112.30
Purchase #3	$119.99	6.632%	$127.9477	$127.95	$127.95	$127.90
Purchase #4	$228.77	7.790%	$246.5912	$246.59	$246.60	$246.60
Purchase #5	$28.75	12.806%	$32.4317	$32.43	$32.45	$32.40
Purchase #6	$143.69	5.360%	$151.3918	$151.39	$151.40	$151.40
Purchase #7	$55.59	5.778%	$58.802	$58.80	$58.80	$58.80
7 purchase totals =	$813.60		$873.5485	$873.55	$873.60	$873.50