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	$112.55	9.783%	$123.5608	$123.56	$123.55	$123.60
Purchase #2	$62.32	3.360%	$64.414	$64.41	$64.40	$64.40
Purchase #3	$129.35	6.518%	$137.781	$137.78	$137.80	$137.80
Purchase #4	$166.98	8.546%	$181.2501	$181.25	$181.25	$181.30
Purchase #5	$71.97	12.442%	$80.9245	$80.92	$80.90	$80.90
Purchase #6	$57.46	13.640%	$65.2975	$65.30	$65.30	$65.30
Purchase #7	$37.50	8.492%	$40.6845	$40.68	$40.70	$40.70
7 purchase totals =	$638.13		$693.9124	$693.90	$693.90	$694.00