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	$73.75	11.462%	$82.2032	$82.20	$82.20	$82.20
Purchase #2	$65.90	8.723%	$71.6485	$71.65	$71.65	$71.60
Purchase #3	$68.48	5.295%	$72.106	$72.11	$72.10	$72.10
Purchase #4	$248.62	9.560%	$272.3881	$272.39	$272.40	$272.40
Purchase #5	$29.67	12.109%	$33.2627	$33.26	$33.25	$33.30
Purchase #6	$28.48	12.280%	$31.9773	$31.98	$32.00	$32.00
Purchase #7	$39.62	10.269%	$43.6886	$43.69	$43.70	$43.70
7 purchase totals =	$554.52		$607.2744	$607.28	$607.30	$607.30