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	$29.33	10.477%	$32.4029	$32.40	$32.40	$32.40
Purchase #2	$73.62	6.754%	$78.5923	$78.59	$78.60	$78.60
Purchase #3	$162.75	3.153%	$167.8815	$167.88	$167.90	$167.90
Purchase #4	$50.88	6.275%	$54.0727	$54.07	$54.05	$54.10
Purchase #5	$147.65	11.213%	$164.206	$164.21	$164.20	$164.20
Purchase #6	$209.57	8.121%	$226.5892	$226.59	$226.60	$226.60
Purchase #7	$181.43	5.798%	$191.9493	$191.95	$191.95	$191.90
7 purchase totals =	$855.23		$915.6939	$915.69	$915.70	$915.70