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	$85.73	12.146%	$96.1428	$96.14	$96.15	$96.10
Purchase #2	$34.31	7.311%	$36.8184	$36.82	$36.80	$36.80
Purchase #3	$35.98	4.819%	$37.7139	$37.71	$37.70	$37.70
Purchase #4	$100.40	11.262%	$111.707	$111.71	$111.70	$111.70
Purchase #5	$109.98	12.608%	$123.8463	$123.85	$123.85	$123.80
Purchase #6	$197.46	10.456%	$218.1064	$218.11	$218.10	$218.10
Purchase #7	$68.80	5.443%	$72.5448	$72.54	$72.55	$72.50
7 purchase totals =	$632.66		$696.8796	$696.88	$696.85	$696.70