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	$241.31	11.665%	$269.4588	$269.46	$269.45	$269.50
Purchase #2	$82.28	4.278%	$85.7999	$85.80	$85.80	$85.80
Purchase #3	$49.54	12.176%	$55.572	$55.57	$55.55	$55.60
Purchase #4	$130.79	8.205%	$141.5213	$141.52	$141.50	$141.50
Purchase #5	$166.31	6.302%	$176.7909	$176.79	$176.80	$176.80
Purchase #6	$166.64	7.661%	$179.4063	$179.41	$179.40	$179.40
Purchase #7	$89.26	10.386%	$98.5305	$98.53	$98.55	$98.50
7 purchase totals =	$926.13		$1,007.0797	$1,007.08	$1,007.05	$1,007.10