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	$128.79	9.342%	$140.8216	$140.82	$140.80	$140.80
Purchase #2	$127.76	10.646%	$141.3613	$141.36	$141.35	$141.40
Purchase #3	$127.37	10.698%	$140.996	$141.00	$141.00	$141.00
Purchase #4	$100.74	12.527%	$113.3597	$113.36	$113.35	$113.40
Purchase #5	$190.89	6.781%	$203.8343	$203.83	$203.85	$203.80
Purchase #6	$176.58	4.873%	$185.1847	$185.18	$185.20	$185.20
Purchase #7	$83.33	3.867%	$86.5524	$86.55	$86.55	$86.60
7 purchase totals =	$935.46		$1,012.1100	$1,012.10	$1,012.10	$1,012.20