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	$73.74	12.314%	$82.8203	$82.82	$82.80	$82.80
Purchase #2	$11.48	8.755%	$12.4851	$12.49	$12.50	$12.50
Purchase #3	$99.40	5.570%	$104.9366	$104.94	$104.95	$104.90
Purchase #4	$47.78	11.193%	$53.128	$53.13	$53.15	$53.10
Purchase #5	$182.68	7.675%	$196.7007	$196.70	$196.70	$196.70
Purchase #6	$129.83	7.222%	$139.2063	$139.21	$139.20	$139.20
Purchase #7	$108.49	8.505%	$117.7171	$117.72	$117.70	$117.70
7 purchase totals =	$653.40		$706.9941	$707.01	$707.00	$706.90