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	$98.37	12.850%	$111.0105	$111.01	$111.00	$111.00
Purchase #2	$210.70	5.395%	$222.0673	$222.07	$222.05	$222.10
Purchase #3	$113.39	6.685%	$120.9701	$120.97	$120.95	$121.00
Purchase #4	$63.76	13.673%	$72.4779	$72.48	$72.50	$72.50
Purchase #5	$149.45	10.661%	$165.3829	$165.38	$165.40	$165.40
Purchase #6	$227.56	7.313%	$244.2015	$244.20	$244.20	$244.20
Purchase #7	$48.31	5.123%	$50.7849	$50.78	$50.80	$50.80
7 purchase totals =	$911.54		$986.8951	$986.89	$986.90	$987.00