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	$197.69	3.661%	$204.9274	$204.93	$204.95	$204.90
Purchase #2	$162.53	3.871%	$168.8215	$168.82	$168.80	$168.80
Purchase #3	$240.70	6.146%	$255.4934	$255.49	$255.50	$255.50
Purchase #4	$153.88	5.571%	$162.4527	$162.45	$162.45	$162.50
Purchase #5	$109.97	7.283%	$117.9791	$117.98	$118.00	$118.00
Purchase #6	$212.40	4.353%	$221.6458	$221.65	$221.65	$221.60
Purchase #7	$151.33	7.322%	$162.4104	$162.41	$162.40	$162.40
7 purchase totals =	$1,228.50		$1,293.7303	$1,293.73	$1,293.75	$1,293.70