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	$171.61	12.361%	$192.8227	$192.82	$192.80	$192.80
Purchase #2	$95.48	4.577%	$99.8501	$99.85	$99.85	$99.90
Purchase #3	$84.28	9.703%	$92.4577	$92.46	$92.45	$92.50
Purchase #4	$225.86	13.542%	$256.446	$256.45	$256.45	$256.40
Purchase #5	$223.47	9.629%	$244.9879	$244.99	$245.00	$245.00
Purchase #6	$104.88	8.648%	$113.95	$113.95	$113.95	$114.00
Purchase #7	$135.88	6.354%	$144.5138	$144.51	$144.50	$144.50
7 purchase totals =	$1,041.46		$1,145.0282	$1,145.03	$1,145.00	$1,145.10