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	$85.50	8.166%	$92.4819	$92.48	$92.50	$92.50
Purchase #2	$213.90	7.503%	$229.9489	$229.95	$229.95	$229.90
Purchase #3	$127.46	5.238%	$134.1364	$134.14	$134.15	$134.10
Purchase #4	$47.86	13.584%	$54.3613	$54.36	$54.35	$54.40
Purchase #5	$136.38	3.811%	$141.5774	$141.58	$141.60	$141.60
Purchase #6	$245.98	5.262%	$258.9235	$258.92	$258.90	$258.90
Purchase #7	$184.64	8.558%	$200.4415	$200.44	$200.45	$200.40
7 purchase totals =	$1,041.72		$1,111.8709	$1,111.87	$1,111.90	$1,111.80