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	$61.63	6.492%	$65.631	$65.63	$65.65	$65.60
Purchase #2	$129.63	6.721%	$138.3424	$138.34	$138.35	$138.30
Purchase #3	$91.43	10.305%	$100.8519	$100.85	$100.85	$100.90
Purchase #4	$221.25	5.267%	$232.9032	$232.90	$232.90	$232.90
Purchase #5	$236.63	10.724%	$262.0062	$262.01	$262.00	$262.00
Purchase #6	$172.93	9.821%	$189.9135	$189.91	$189.90	$189.90
Purchase #7	$90.55	10.238%	$99.8205	$99.82	$99.80	$99.80
7 purchase totals =	$1,004.05		$1,089.4687	$1,089.46	$1,089.45	$1,089.40