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	$130.88	9.182%	$142.8974	$142.90	$142.90	$142.90
Purchase #2	$67.67	7.454%	$72.7141	$72.71	$72.70	$72.70
Purchase #3	$50.74	3.771%	$52.6534	$52.65	$52.65	$52.70
Purchase #4	$132.53	13.760%	$150.7661	$150.77	$150.75	$150.80
Purchase #5	$177.80	10.258%	$196.0387	$196.04	$196.05	$196.00
Purchase #6	$69.84	3.253%	$72.1119	$72.11	$72.10	$72.10
Purchase #7	$23.97	7.615%	$25.7953	$25.80	$25.80	$25.80
7 purchase totals =	$653.43		$712.9769	$712.98	$712.95	$713.00