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	$152.62	6.604%	$162.699	$162.70	$162.70	$162.70
Purchase #2	$136.48	11.747%	$152.5123	$152.51	$152.50	$152.50
Purchase #3	$76.75	12.479%	$86.3276	$86.33	$86.35	$86.30
Purchase #4	$71.89	6.244%	$76.3788	$76.38	$76.40	$76.40
Purchase #5	$69.39	6.376%	$73.8143	$73.81	$73.80	$73.80
Purchase #6	$80.41	11.692%	$89.8115	$89.81	$89.80	$89.80
Purchase #7	$219.59	8.633%	$238.5472	$238.55	$238.55	$238.50
7 purchase totals =	$807.13		$880.0907	$880.09	$880.10	$880.00