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	$222.97	5.699%	$235.6771	$235.68	$235.70	$235.70
Purchase #2	$90.59	13.858%	$103.144	$103.14	$103.15	$103.10
Purchase #3	$182.68	9.212%	$199.5085	$199.51	$199.50	$199.50
Purchase #4	$246.41	3.575%	$255.2192	$255.22	$255.20	$255.20
Purchase #5	$236.39	12.686%	$266.3784	$266.38	$266.40	$266.40
Purchase #6	$70.46	3.132%	$72.6668	$72.67	$72.65	$72.70
Purchase #7	$223.51	7.500%	$240.2733	$240.27	$240.25	$240.30
7 purchase totals =	$1,273.01		$1,372.8673	$1,372.87	$1,372.85	$1,372.90