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	$239.55	7.113%	$256.5892	$256.59	$256.60	$256.60
Purchase #2	$250.45	3.457%	$259.1081	$259.11	$259.10	$259.10
Purchase #3	$53.90	10.320%	$59.4625	$59.46	$59.45	$59.50
Purchase #4	$237.84	8.199%	$257.3405	$257.34	$257.35	$257.30
Purchase #5	$141.82	10.147%	$156.2105	$156.21	$156.20	$156.20
Purchase #6	$141.33	7.352%	$151.7206	$151.72	$151.70	$151.70
Purchase #7	$222.96	6.174%	$236.7256	$236.73	$236.75	$236.70
7 purchase totals =	$1,287.85		$1,377.1570	$1,377.16	$1,377.15	$1,377.10