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	$243.90	6.575%	$259.9364	$259.94	$259.95	$259.90
Purchase #2	$181.65	10.346%	$200.4435	$200.44	$200.45	$200.40
Purchase #3	$139.89	7.577%	$150.4895	$150.49	$150.50	$150.50
Purchase #4	$238.29	3.813%	$247.376	$247.38	$247.40	$247.40
Purchase #5	$223.57	5.345%	$235.5198	$235.52	$235.50	$235.50
Purchase #6	$189.83	8.506%	$205.9769	$205.98	$206.00	$206.00
Purchase #7	$104.82	6.856%	$112.0065	$112.01	$112.00	$112.00
7 purchase totals =	$1,321.95		$1,411.7486	$1,411.76	$1,411.80	$1,411.70