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	$197.56	10.352%	$218.0114	$218.01	$218.00	$218.00
Purchase #2	$47.62	8.259%	$51.5529	$51.55	$51.55	$51.60
Purchase #3	$31.90	9.613%	$34.9665	$34.97	$34.95	$35.00
Purchase #4	$57.48	3.317%	$59.3866	$59.39	$59.40	$59.40
Purchase #5	$206.39	11.297%	$229.7059	$229.71	$229.70	$229.70
Purchase #6	$171.84	8.459%	$186.3759	$186.38	$186.40	$186.40
Purchase #7	$80.85	12.464%	$90.9271	$90.93	$90.95	$90.90
7 purchase totals =	$793.64		$870.9263	$870.94	$870.95	$871.00