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	$248.32	4.123%	$258.5582	$258.56	$258.55	$258.60
Purchase #2	$150.50	3.837%	$156.2747	$156.27	$156.25	$156.30
Purchase #3	$104.45	4.624%	$109.2798	$109.28	$109.30	$109.30
Purchase #4	$119.92	9.645%	$131.4863	$131.49	$131.50	$131.50
Purchase #5	$214.95	3.405%	$222.269	$222.27	$222.25	$222.30
Purchase #6	$194.55	12.695%	$219.2481	$219.25	$219.25	$219.20
Purchase #7	$190.66	10.861%	$211.3676	$211.37	$211.35	$211.40
7 purchase totals =	$1,223.35		$1,308.4837	$1,308.49	$1,308.45	$1,308.60