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	$172.96	4.545%	$180.821	$180.82	$180.80	$180.80
Purchase #2	$80.62	11.334%	$89.7575	$89.76	$89.75	$89.80
Purchase #3	$105.31	7.867%	$113.5947	$113.59	$113.60	$113.60
Purchase #4	$143.81	5.183%	$151.2637	$151.26	$151.25	$151.30
Purchase #5	$174.36	7.200%	$186.9139	$186.91	$186.90	$186.90
Purchase #6	$49.82	11.820%	$55.7087	$55.71	$55.70	$55.70
Purchase #7	$213.31	7.866%	$230.089	$230.09	$230.10	$230.10
7 purchase totals =	$940.19		$1,008.1485	$1,008.14	$1,008.10	$1,008.20