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	$32.74	7.659%	$35.2476	$35.25	$35.25	$35.20
Purchase #2	$97.54	5.623%	$103.0247	$103.02	$103.00	$103.00
Purchase #3	$128.64	3.243%	$132.8118	$132.81	$132.80	$132.80
Purchase #4	$85.41	11.118%	$94.9059	$94.91	$94.90	$94.90
Purchase #5	$98.37	4.708%	$103.0013	$103.00	$103.00	$103.00
Purchase #6	$99.58	12.134%	$111.663	$111.66	$111.65	$111.70
Purchase #7	$109.61	12.274%	$123.0635	$123.06	$123.05	$123.10
7 purchase totals =	$651.89		$703.7178	$703.71	$703.65	$703.70