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	$178.95	5.829%	$189.381	$189.38	$189.40	$189.40
Purchase #2	$6.98	9.380%	$7.6347	$7.63	$7.65	$7.60
Purchase #3	$64.85	9.632%	$71.0964	$71.10	$71.10	$71.10
Purchase #4	$248.36	13.857%	$282.7752	$282.78	$282.80	$282.80
Purchase #5	$43.39	4.410%	$45.3035	$45.30	$45.30	$45.30
Purchase #6	$34.81	12.862%	$39.2873	$39.29	$39.30	$39.30
Purchase #7	$224.53	9.298%	$245.4068	$245.41	$245.40	$245.40
7 purchase totals =	$801.87		$880.8849	$880.89	$880.95	$880.90