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	$74.31	12.159%	$83.3454	$83.35	$83.35	$83.30
Purchase #2	$125.27	9.426%	$137.078	$137.08	$137.10	$137.10
Purchase #3	$124.27	5.245%	$130.788	$130.79	$130.80	$130.80
Purchase #4	$38.49	12.858%	$43.439	$43.44	$43.45	$43.40
Purchase #5	$181.30	8.175%	$196.1213	$196.12	$196.10	$196.10
Purchase #6	$250.92	12.614%	$282.571	$282.57	$282.55	$282.60
Purchase #7	$181.40	12.397%	$203.8882	$203.89	$203.90	$203.90
7 purchase totals =	$975.96		$1,077.2309	$1,077.24	$1,077.25	$1,077.20