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	$126.72	12.589%	$142.6728	$142.67	$142.65	$142.70
Purchase #2	$95.77	4.305%	$99.8929	$99.89	$99.90	$99.90
Purchase #3	$193.74	9.403%	$211.9574	$211.96	$211.95	$212.00
Purchase #4	$102.26	10.121%	$112.6097	$112.61	$112.60	$112.60
Purchase #5	$187.49	8.774%	$203.9404	$203.94	$203.95	$203.90
Purchase #6	$44.94	6.303%	$47.7726	$47.77	$47.75	$47.80
Purchase #7	$119.35	3.537%	$123.5714	$123.57	$123.55	$123.60
7 purchase totals =	$870.27		$942.4172	$942.41	$942.35	$942.50