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	$33.47	6.398%	$35.6114	$35.61	$35.60	$35.60
Purchase #2	$35.39	9.533%	$38.7637	$38.76	$38.75	$38.80
Purchase #3	$45.47	7.298%	$48.7884	$48.79	$48.80	$48.80
Purchase #4	$139.46	10.469%	$154.0601	$154.06	$154.05	$154.10
Purchase #5	$28.91	8.205%	$31.2821	$31.28	$31.30	$31.30
Purchase #6	$104.26	5.116%	$109.5939	$109.59	$109.60	$109.60
Purchase #7	$88.57	6.429%	$94.2642	$94.26	$94.25	$94.30
7 purchase totals =	$475.53		$512.3638	$512.35	$512.35	$512.50