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	$23.58	6.558%	$25.1264	$25.13	$25.15	$25.10
Purchase #2	$240.71	6.630%	$256.6691	$256.67	$256.65	$256.70
Purchase #3	$242.61	8.651%	$263.5982	$263.60	$263.60	$263.60
Purchase #4	$159.81	5.680%	$168.8872	$168.89	$168.90	$168.90
Purchase #5	$58.97	11.301%	$65.6342	$65.63	$65.65	$65.60
Purchase #6	$133.89	13.369%	$151.7898	$151.79	$151.80	$151.80
Purchase #7	$122.38	3.681%	$126.8848	$126.88	$126.90	$126.90
7 purchase totals =	$981.95		$1,058.5897	$1,058.59	$1,058.65	$1,058.60