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	$56.54	10.604%	$62.5355	$62.54	$62.55	$62.50
Purchase #2	$79.43	13.751%	$90.3524	$90.35	$90.35	$90.40
Purchase #3	$120.76	3.416%	$124.8852	$124.89	$124.90	$124.90
Purchase #4	$143.33	12.287%	$160.941	$160.94	$160.95	$160.90
Purchase #5	$232.64	7.493%	$250.0717	$250.07	$250.05	$250.10
Purchase #6	$227.36	12.149%	$254.982	$254.98	$255.00	$255.00
Purchase #7	$70.40	13.247%	$79.7259	$79.73	$79.75	$79.70
7 purchase totals =	$930.46		$1,023.4937	$1,023.50	$1,023.55	$1,023.50