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	$97.82	13.634%	$111.1568	$111.16	$111.15	$111.20
Purchase #2	$193.90	13.436%	$219.9524	$219.95	$219.95	$220.00
Purchase #3	$68.65	10.642%	$75.9557	$75.96	$75.95	$76.00
Purchase #4	$181.40	10.403%	$200.271	$200.27	$200.25	$200.30
Purchase #5	$234.58	3.111%	$241.8778	$241.88	$241.90	$241.90
Purchase #6	$81.84	9.594%	$89.6917	$89.69	$89.70	$89.70
Purchase #7	$184.36	12.577%	$207.547	$207.55	$207.55	$207.50
7 purchase totals =	$1,042.55		$1,146.4524	$1,146.46	$1,146.45	$1,146.60