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	$59.33	13.542%	$67.3645	$67.36	$67.35	$67.40
Purchase #2	$80.77	3.384%	$83.5033	$83.50	$83.50	$83.50
Purchase #3	$232.56	6.545%	$247.7811	$247.78	$247.80	$247.80
Purchase #4	$194.51	3.692%	$201.6913	$201.69	$201.70	$201.70
Purchase #5	$242.82	12.564%	$273.3279	$273.33	$273.35	$273.30
Purchase #6	$34.60	13.527%	$39.2803	$39.28	$39.30	$39.30
Purchase #7	$99.57	11.488%	$111.0086	$111.01	$111.00	$111.00
7 purchase totals =	$944.16		$1,023.9570	$1,023.95	$1,024.00	$1,024.00