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	$82.77	8.114%	$89.486	$89.49	$89.50	$89.50
Purchase #2	$215.67	13.314%	$244.3843	$244.38	$244.40	$244.40
Purchase #3	$240.56	5.630%	$254.1035	$254.10	$254.10	$254.10
Purchase #4	$187.65	13.329%	$212.6619	$212.66	$212.65	$212.70
Purchase #5	$149.39	3.123%	$154.0554	$154.06	$154.05	$154.10
Purchase #6	$197.89	12.215%	$222.0623	$222.06	$222.05	$222.10
Purchase #7	$227.98	13.593%	$258.9693	$258.97	$258.95	$259.00
7 purchase totals =	$1,301.91		$1,435.7227	$1,435.72	$1,435.70	$1,435.90