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	$233.57	11.692%	$260.879	$260.88	$260.90	$260.90
Purchase #2	$226.31	3.533%	$234.3055	$234.31	$234.30	$234.30
Purchase #3	$244.30	7.802%	$263.3603	$263.36	$263.35	$263.40
Purchase #4	$65.26	8.253%	$70.6459	$70.65	$70.65	$70.60
Purchase #5	$54.27	9.342%	$59.3399	$59.34	$59.35	$59.30
Purchase #6	$69.69	13.238%	$78.9156	$78.92	$78.90	$78.90
Purchase #7	$43.66	10.539%	$48.2613	$48.26	$48.25	$48.30
7 purchase totals =	$937.06		$1,015.7075	$1,015.72	$1,015.70	$1,015.70