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	$107.86	3.162%	$111.2705	$111.27	$111.25	$111.30
Purchase #2	$235.60	8.240%	$255.0134	$255.01	$255.00	$255.00
Purchase #3	$67.51	3.129%	$69.6224	$69.62	$69.60	$69.60
Purchase #4	$112.64	6.790%	$120.2883	$120.29	$120.30	$120.30
Purchase #5	$132.77	9.172%	$144.9477	$144.95	$144.95	$144.90
Purchase #6	$143.43	6.642%	$152.9566	$152.96	$152.95	$153.00
Purchase #7	$179.73	9.130%	$196.1393	$196.14	$196.15	$196.10
7 purchase totals =	$979.54		$1,050.2382	$1,050.24	$1,050.20	$1,050.20