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	$132.39	6.618%	$141.1516	$141.15	$141.15	$141.20
Purchase #2	$125.33	4.615%	$131.114	$131.11	$131.10	$131.10
Purchase #3	$121.73	13.171%	$137.7631	$137.76	$137.75	$137.80
Purchase #4	$35.67	13.229%	$40.3888	$40.39	$40.40	$40.40
Purchase #5	$126.92	3.547%	$131.4219	$131.42	$131.40	$131.40
Purchase #6	$55.89	6.647%	$59.605	$59.61	$59.60	$59.60
Purchase #7	$77.45	5.480%	$81.6943	$81.69	$81.70	$81.70
7 purchase totals =	$675.38		$723.1387	$723.13	$723.10	$723.20