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	$182.64	3.735%	$189.4616	$189.46	$189.45	$189.50
Purchase #2	$144.90	4.182%	$150.9597	$150.96	$150.95	$151.00
Purchase #3	$167.79	10.622%	$185.6127	$185.61	$185.60	$185.60
Purchase #4	$29.74	9.400%	$32.5356	$32.54	$32.55	$32.50
Purchase #5	$128.40	9.870%	$141.0731	$141.07	$141.05	$141.10
Purchase #6	$114.73	7.554%	$123.3967	$123.40	$123.40	$123.40
Purchase #7	$109.97	4.322%	$114.7229	$114.72	$114.70	$114.70
7 purchase totals =	$878.17		$937.7623	$937.76	$937.70	$937.80