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	$39.32	10.711%	$43.5316	$43.53	$43.55	$43.50
Purchase #2	$230.40	12.650%	$259.5456	$259.55	$259.55	$259.50
Purchase #3	$206.67	4.267%	$215.4886	$215.49	$215.50	$215.50
Purchase #4	$111.41	7.293%	$119.5351	$119.54	$119.55	$119.50
Purchase #5	$81.39	7.515%	$87.5065	$87.51	$87.50	$87.50
Purchase #6	$128.46	4.392%	$134.102	$134.10	$134.10	$134.10
Purchase #7	$12.60	13.618%	$14.3159	$14.32	$14.30	$14.30
7 purchase totals =	$810.25		$874.0253	$874.04	$874.05	$873.90