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	$63.59	11.663%	$71.0065	$71.01	$71.00	$71.00
Purchase #2	$101.51	11.225%	$112.9045	$112.90	$112.90	$112.90
Purchase #3	$190.63	4.844%	$199.8641	$199.86	$199.85	$199.90
Purchase #4	$146.35	9.816%	$160.7157	$160.72	$160.70	$160.70
Purchase #5	$184.95	6.565%	$197.092	$197.09	$197.10	$197.10
Purchase #6	$192.28	11.160%	$213.7384	$213.74	$213.75	$213.70
Purchase #7	$86.63	4.482%	$90.5128	$90.51	$90.50	$90.50
7 purchase totals =	$965.94		$1,045.8340	$1,045.83	$1,045.80	$1,045.80