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	$191.57	13.737%	$217.886	$217.89	$217.90	$217.90
Purchase #2	$119.69	9.750%	$131.3598	$131.36	$131.35	$131.40
Purchase #3	$206.98	9.755%	$227.1709	$227.17	$227.15	$227.20
Purchase #4	$155.82	10.108%	$171.5703	$171.57	$171.55	$171.60
Purchase #5	$141.61	13.243%	$160.3634	$160.36	$160.35	$160.40
Purchase #6	$153.72	13.818%	$174.961	$174.96	$174.95	$175.00
Purchase #7	$139.96	8.404%	$151.7222	$151.72	$151.70	$151.70
7 purchase totals =	$1,109.35		$1,235.0336	$1,235.03	$1,234.95	$1,235.20