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	$242.50	4.154%	$252.5735	$252.57	$252.55	$252.60
Purchase #2	$249.54	12.335%	$280.3208	$280.32	$280.30	$280.30
Purchase #3	$218.47	4.343%	$227.9582	$227.96	$227.95	$228.00
Purchase #4	$106.62	11.578%	$118.9645	$118.96	$118.95	$119.00
Purchase #5	$149.67	4.666%	$156.6536	$156.65	$156.65	$156.70
Purchase #6	$37.34	8.594%	$40.549	$40.55	$40.55	$40.50
Purchase #7	$179.58	3.469%	$185.8096	$185.81	$185.80	$185.80
7 purchase totals =	$1,183.72		$1,262.8292	$1,262.82	$1,262.75	$1,262.90