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	$62.47	5.439%	$65.8677	$65.87	$65.85	$65.90
Purchase #2	$38.56	12.680%	$43.4494	$43.45	$43.45	$43.40
Purchase #3	$229.86	5.476%	$242.4471	$242.45	$242.45	$242.40
Purchase #4	$245.89	7.179%	$263.5424	$263.54	$263.55	$263.50
Purchase #5	$92.26	12.329%	$103.6347	$103.63	$103.65	$103.60
Purchase #6	$48.34	10.517%	$53.4239	$53.42	$53.40	$53.40
Purchase #7	$127.94	3.194%	$132.0264	$132.03	$132.05	$132.00
7 purchase totals =	$845.32		$904.3916	$904.39	$904.40	$904.20