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	$161.63	7.779%	$174.2032	$174.20	$174.20	$174.20
Purchase #2	$227.92	12.185%	$255.6921	$255.69	$255.70	$255.70
Purchase #3	$227.53	12.258%	$255.4206	$255.42	$255.40	$255.40
Purchase #4	$39.60	9.666%	$43.4277	$43.43	$43.45	$43.40
Purchase #5	$163.68	5.207%	$172.2028	$172.20	$172.20	$172.20
Purchase #6	$50.82	13.241%	$57.5491	$57.55	$57.55	$57.50
Purchase #7	$151.85	13.857%	$172.8919	$172.89	$172.90	$172.90
7 purchase totals =	$1,023.03		$1,131.3874	$1,131.38	$1,131.40	$1,131.30