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	$224.64	9.755%	$246.5536	$246.55	$246.55	$246.60
Purchase #2	$107.55	3.851%	$111.6918	$111.69	$111.70	$111.70
Purchase #3	$142.27	10.361%	$157.0106	$157.01	$157.00	$157.00
Purchase #4	$56.73	9.624%	$62.1897	$62.19	$62.20	$62.20
Purchase #5	$73.64	9.645%	$80.7426	$80.74	$80.75	$80.70
Purchase #6	$48.66	9.528%	$53.2963	$53.30	$53.30	$53.30
Purchase #7	$54.54	9.696%	$59.8282	$59.83	$59.85	$59.80
7 purchase totals =	$708.03		$771.3128	$771.31	$771.35	$771.30