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	$152.27	6.401%	$162.0168	$162.02	$162.00	$162.00
Purchase #2	$211.34	6.604%	$225.2969	$225.30	$225.30	$225.30
Purchase #3	$130.93	3.399%	$135.3803	$135.38	$135.40	$135.40
Purchase #4	$99.86	5.201%	$105.0537	$105.05	$105.05	$105.10
Purchase #5	$246.86	6.509%	$262.9281	$262.93	$262.95	$262.90
Purchase #6	$247.58	13.455%	$280.8919	$280.89	$280.90	$280.90
Purchase #7	$111.34	7.360%	$119.5346	$119.53	$119.55	$119.50
7 purchase totals =	$1,200.18		$1,291.1023	$1,291.10	$1,291.15	$1,291.10