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	$53.98	3.496%	$55.8671	$55.87	$55.85	$55.90
Purchase #2	$85.61	10.167%	$94.314	$94.31	$94.30	$94.30
Purchase #3	$83.45	12.791%	$94.1241	$94.12	$94.10	$94.10
Purchase #4	$215.80	8.689%	$234.5509	$234.55	$234.55	$234.60
Purchase #5	$112.89	3.586%	$116.9382	$116.94	$116.95	$116.90
Purchase #6	$89.93	5.522%	$94.8959	$94.90	$94.90	$94.90
Purchase #7	$35.56	13.494%	$40.3585	$40.36	$40.35	$40.40
7 purchase totals =	$677.22		$731.0487	$731.05	$731.00	$731.10