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	$107.81	5.725%	$113.9821	$113.98	$114.00	$114.00
Purchase #2	$72.66	11.289%	$80.8626	$80.86	$80.85	$80.90
Purchase #3	$120.49	3.408%	$124.5963	$124.60	$124.60	$124.60
Purchase #4	$54.80	3.310%	$56.6139	$56.61	$56.60	$56.60
Purchase #5	$203.31	12.829%	$229.3926	$229.39	$229.40	$229.40
Purchase #6	$61.56	9.598%	$67.4685	$67.47	$67.45	$67.50
Purchase #7	$125.57	9.534%	$137.5418	$137.54	$137.55	$137.50
7 purchase totals =	$746.20		$810.4578	$810.45	$810.45	$810.50