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	$200.43	12.756%	$225.9969	$226.00	$226.00	$226.00
Purchase #2	$52.97	9.118%	$57.7998	$57.80	$57.80	$57.80
Purchase #3	$69.76	3.554%	$72.2393	$72.24	$72.25	$72.20
Purchase #4	$172.42	12.516%	$194.0001	$194.00	$194.00	$194.00
Purchase #5	$225.46	13.297%	$255.4394	$255.44	$255.45	$255.40
Purchase #6	$83.55	8.321%	$90.5022	$90.50	$90.50	$90.50
Purchase #7	$170.32	13.561%	$193.4171	$193.42	$193.40	$193.40
7 purchase totals =	$974.91		$1,089.3948	$1,089.40	$1,089.40	$1,089.30